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59bd9ded 1// SPDX-License-Identifier: GPL-2.0-only
1da177e4
LT
2/*
3 * linux/fs/namespace.c
4 *
5 * (C) Copyright Al Viro 2000, 2001
1da177e4
LT
6 *
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
8 * Heavily rewritten.
9 */
10
1da177e4 11#include <linux/syscalls.h>
d10577a8 12#include <linux/export.h>
16f7e0fe 13#include <linux/capability.h>
6b3286ed 14#include <linux/mnt_namespace.h>
771b1371 15#include <linux/user_namespace.h>
1da177e4
LT
16#include <linux/namei.h>
17#include <linux/security.h>
5b825c3a 18#include <linux/cred.h>
73cd49ec 19#include <linux/idr.h>
57f150a5 20#include <linux/init.h> /* init_rootfs */
d10577a8
AV
21#include <linux/fs_struct.h> /* get_fs_root et.al. */
22#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
a07b2000 23#include <linux/file.h>
d10577a8 24#include <linux/uaccess.h>
0bb80f24 25#include <linux/proc_ns.h>
20b4fb48 26#include <linux/magic.h>
57c8a661 27#include <linux/memblock.h>
9caccd41 28#include <linux/proc_fs.h>
9ea459e1 29#include <linux/task_work.h>
9164bb4a 30#include <linux/sched/task.h>
e262e32d 31#include <uapi/linux/mount.h>
9bc61ab1 32#include <linux/fs_context.h>
037f11b4 33#include <linux/shmem_fs.h>
9164bb4a 34
07b20889 35#include "pnode.h"
948730b0 36#include "internal.h"
1da177e4 37
d2921684
EB
38/* Maximum number of mounts in a mount namespace */
39unsigned int sysctl_mount_max __read_mostly = 100000;
40
0818bf27
AV
41static unsigned int m_hash_mask __read_mostly;
42static unsigned int m_hash_shift __read_mostly;
43static unsigned int mp_hash_mask __read_mostly;
44static unsigned int mp_hash_shift __read_mostly;
45
46static __initdata unsigned long mhash_entries;
47static int __init set_mhash_entries(char *str)
48{
49 if (!str)
50 return 0;
51 mhash_entries = simple_strtoul(str, &str, 0);
52 return 1;
53}
54__setup("mhash_entries=", set_mhash_entries);
55
56static __initdata unsigned long mphash_entries;
57static int __init set_mphash_entries(char *str)
58{
59 if (!str)
60 return 0;
61 mphash_entries = simple_strtoul(str, &str, 0);
62 return 1;
63}
64__setup("mphash_entries=", set_mphash_entries);
13f14b4d 65
c7999c36 66static u64 event;
73cd49ec 67static DEFINE_IDA(mnt_id_ida);
719f5d7f 68static DEFINE_IDA(mnt_group_ida);
1da177e4 69
38129a13 70static struct hlist_head *mount_hashtable __read_mostly;
0818bf27 71static struct hlist_head *mountpoint_hashtable __read_mostly;
e18b890b 72static struct kmem_cache *mnt_cache __read_mostly;
59aa0da8 73static DECLARE_RWSEM(namespace_sem);
4edbe133
AV
74static HLIST_HEAD(unmounted); /* protected by namespace_sem */
75static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
1da177e4 76
2a186721
CB
77struct mount_kattr {
78 unsigned int attr_set;
79 unsigned int attr_clr;
80 unsigned int propagation;
81 unsigned int lookup_flags;
82 bool recurse;
9caccd41 83 struct user_namespace *mnt_userns;
2a186721
CB
84};
85
f87fd4c2 86/* /sys/fs */
00d26666
GKH
87struct kobject *fs_kobj;
88EXPORT_SYMBOL_GPL(fs_kobj);
f87fd4c2 89
99b7db7b
NP
90/*
91 * vfsmount lock may be taken for read to prevent changes to the
92 * vfsmount hash, ie. during mountpoint lookups or walking back
93 * up the tree.
94 *
95 * It should be taken for write in all cases where the vfsmount
96 * tree or hash is modified or when a vfsmount structure is modified.
97 */
48a066e7 98__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
99b7db7b 99
d033cb67
CB
100static inline void lock_mount_hash(void)
101{
102 write_seqlock(&mount_lock);
103}
104
105static inline void unlock_mount_hash(void)
106{
107 write_sequnlock(&mount_lock);
108}
109
38129a13 110static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
1da177e4 111{
b58fed8b
RP
112 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
113 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
0818bf27
AV
114 tmp = tmp + (tmp >> m_hash_shift);
115 return &mount_hashtable[tmp & m_hash_mask];
116}
117
118static inline struct hlist_head *mp_hash(struct dentry *dentry)
119{
120 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
121 tmp = tmp + (tmp >> mp_hash_shift);
122 return &mountpoint_hashtable[tmp & mp_hash_mask];
1da177e4
LT
123}
124
b105e270 125static int mnt_alloc_id(struct mount *mnt)
73cd49ec 126{
169b480e
MW
127 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
128
129 if (res < 0)
130 return res;
131 mnt->mnt_id = res;
132 return 0;
73cd49ec
MS
133}
134
b105e270 135static void mnt_free_id(struct mount *mnt)
73cd49ec 136{
169b480e 137 ida_free(&mnt_id_ida, mnt->mnt_id);
73cd49ec
MS
138}
139
719f5d7f
MS
140/*
141 * Allocate a new peer group ID
719f5d7f 142 */
4b8b21f4 143static int mnt_alloc_group_id(struct mount *mnt)
719f5d7f 144{
169b480e 145 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
f21f6220 146
169b480e
MW
147 if (res < 0)
148 return res;
149 mnt->mnt_group_id = res;
150 return 0;
719f5d7f
MS
151}
152
153/*
154 * Release a peer group ID
155 */
4b8b21f4 156void mnt_release_group_id(struct mount *mnt)
719f5d7f 157{
169b480e 158 ida_free(&mnt_group_ida, mnt->mnt_group_id);
15169fe7 159 mnt->mnt_group_id = 0;
719f5d7f
MS
160}
161
b3e19d92
NP
162/*
163 * vfsmount lock must be held for read
164 */
83adc753 165static inline void mnt_add_count(struct mount *mnt, int n)
b3e19d92
NP
166{
167#ifdef CONFIG_SMP
68e8a9fe 168 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
b3e19d92
NP
169#else
170 preempt_disable();
68e8a9fe 171 mnt->mnt_count += n;
b3e19d92
NP
172 preempt_enable();
173#endif
174}
175
b3e19d92
NP
176/*
177 * vfsmount lock must be held for write
178 */
edf7ddbf 179int mnt_get_count(struct mount *mnt)
b3e19d92
NP
180{
181#ifdef CONFIG_SMP
edf7ddbf 182 int count = 0;
b3e19d92
NP
183 int cpu;
184
185 for_each_possible_cpu(cpu) {
68e8a9fe 186 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
b3e19d92
NP
187 }
188
189 return count;
190#else
68e8a9fe 191 return mnt->mnt_count;
b3e19d92
NP
192#endif
193}
194
b105e270 195static struct mount *alloc_vfsmnt(const char *name)
1da177e4 196{
c63181e6
AV
197 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
198 if (mnt) {
73cd49ec
MS
199 int err;
200
c63181e6 201 err = mnt_alloc_id(mnt);
88b38782
LZ
202 if (err)
203 goto out_free_cache;
204
205 if (name) {
fcc139ae 206 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL);
c63181e6 207 if (!mnt->mnt_devname)
88b38782 208 goto out_free_id;
73cd49ec
MS
209 }
210
b3e19d92 211#ifdef CONFIG_SMP
c63181e6
AV
212 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
213 if (!mnt->mnt_pcp)
b3e19d92
NP
214 goto out_free_devname;
215
c63181e6 216 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
b3e19d92 217#else
c63181e6
AV
218 mnt->mnt_count = 1;
219 mnt->mnt_writers = 0;
b3e19d92
NP
220#endif
221
38129a13 222 INIT_HLIST_NODE(&mnt->mnt_hash);
c63181e6
AV
223 INIT_LIST_HEAD(&mnt->mnt_child);
224 INIT_LIST_HEAD(&mnt->mnt_mounts);
225 INIT_LIST_HEAD(&mnt->mnt_list);
226 INIT_LIST_HEAD(&mnt->mnt_expire);
227 INIT_LIST_HEAD(&mnt->mnt_share);
228 INIT_LIST_HEAD(&mnt->mnt_slave_list);
229 INIT_LIST_HEAD(&mnt->mnt_slave);
0a5eb7c8 230 INIT_HLIST_NODE(&mnt->mnt_mp_list);
99b19d16 231 INIT_LIST_HEAD(&mnt->mnt_umounting);
56cbb429 232 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
a6435940 233 mnt->mnt.mnt_userns = &init_user_ns;
1da177e4 234 }
c63181e6 235 return mnt;
88b38782 236
d3ef3d73
NP
237#ifdef CONFIG_SMP
238out_free_devname:
fcc139ae 239 kfree_const(mnt->mnt_devname);
d3ef3d73 240#endif
88b38782 241out_free_id:
c63181e6 242 mnt_free_id(mnt);
88b38782 243out_free_cache:
c63181e6 244 kmem_cache_free(mnt_cache, mnt);
88b38782 245 return NULL;
1da177e4
LT
246}
247
3d733633
DH
248/*
249 * Most r/o checks on a fs are for operations that take
250 * discrete amounts of time, like a write() or unlink().
251 * We must keep track of when those operations start
252 * (for permission checks) and when they end, so that
253 * we can determine when writes are able to occur to
254 * a filesystem.
255 */
256/*
257 * __mnt_is_readonly: check whether a mount is read-only
258 * @mnt: the mount to check for its write status
259 *
260 * This shouldn't be used directly ouside of the VFS.
261 * It does not guarantee that the filesystem will stay
262 * r/w, just that it is right *now*. This can not and
263 * should not be used in place of IS_RDONLY(inode).
264 * mnt_want/drop_write() will _keep_ the filesystem
265 * r/w.
266 */
43f5e655 267bool __mnt_is_readonly(struct vfsmount *mnt)
3d733633 268{
43f5e655 269 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
3d733633
DH
270}
271EXPORT_SYMBOL_GPL(__mnt_is_readonly);
272
83adc753 273static inline void mnt_inc_writers(struct mount *mnt)
d3ef3d73
NP
274{
275#ifdef CONFIG_SMP
68e8a9fe 276 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
d3ef3d73 277#else
68e8a9fe 278 mnt->mnt_writers++;
d3ef3d73
NP
279#endif
280}
3d733633 281
83adc753 282static inline void mnt_dec_writers(struct mount *mnt)
3d733633 283{
d3ef3d73 284#ifdef CONFIG_SMP
68e8a9fe 285 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
d3ef3d73 286#else
68e8a9fe 287 mnt->mnt_writers--;
d3ef3d73 288#endif
3d733633 289}
3d733633 290
83adc753 291static unsigned int mnt_get_writers(struct mount *mnt)
3d733633 292{
d3ef3d73
NP
293#ifdef CONFIG_SMP
294 unsigned int count = 0;
3d733633 295 int cpu;
3d733633
DH
296
297 for_each_possible_cpu(cpu) {
68e8a9fe 298 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
3d733633 299 }
3d733633 300
d3ef3d73
NP
301 return count;
302#else
303 return mnt->mnt_writers;
304#endif
3d733633
DH
305}
306
4ed5e82f
MS
307static int mnt_is_readonly(struct vfsmount *mnt)
308{
309 if (mnt->mnt_sb->s_readonly_remount)
310 return 1;
311 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
312 smp_rmb();
313 return __mnt_is_readonly(mnt);
314}
315
8366025e 316/*
eb04c282
JK
317 * Most r/o & frozen checks on a fs are for operations that take discrete
318 * amounts of time, like a write() or unlink(). We must keep track of when
319 * those operations start (for permission checks) and when they end, so that we
320 * can determine when writes are able to occur to a filesystem.
8366025e
DH
321 */
322/**
eb04c282 323 * __mnt_want_write - get write access to a mount without freeze protection
83adc753 324 * @m: the mount on which to take a write
8366025e 325 *
eb04c282
JK
326 * This tells the low-level filesystem that a write is about to be performed to
327 * it, and makes sure that writes are allowed (mnt it read-write) before
328 * returning success. This operation does not protect against filesystem being
329 * frozen. When the write operation is finished, __mnt_drop_write() must be
330 * called. This is effectively a refcount.
8366025e 331 */
eb04c282 332int __mnt_want_write(struct vfsmount *m)
8366025e 333{
83adc753 334 struct mount *mnt = real_mount(m);
3d733633 335 int ret = 0;
3d733633 336
d3ef3d73 337 preempt_disable();
c6653a83 338 mnt_inc_writers(mnt);
d3ef3d73 339 /*
c6653a83 340 * The store to mnt_inc_writers must be visible before we pass
d3ef3d73
NP
341 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
342 * incremented count after it has set MNT_WRITE_HOLD.
343 */
344 smp_mb();
6aa7de05 345 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
d3ef3d73
NP
346 cpu_relax();
347 /*
348 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
349 * be set to match its requirements. So we must not load that until
350 * MNT_WRITE_HOLD is cleared.
351 */
352 smp_rmb();
4ed5e82f 353 if (mnt_is_readonly(m)) {
c6653a83 354 mnt_dec_writers(mnt);
3d733633 355 ret = -EROFS;
3d733633 356 }
d3ef3d73 357 preempt_enable();
eb04c282
JK
358
359 return ret;
360}
361
362/**
363 * mnt_want_write - get write access to a mount
364 * @m: the mount on which to take a write
365 *
366 * This tells the low-level filesystem that a write is about to be performed to
367 * it, and makes sure that writes are allowed (mount is read-write, filesystem
368 * is not frozen) before returning success. When the write operation is
369 * finished, mnt_drop_write() must be called. This is effectively a refcount.
370 */
371int mnt_want_write(struct vfsmount *m)
372{
373 int ret;
374
375 sb_start_write(m->mnt_sb);
376 ret = __mnt_want_write(m);
377 if (ret)
378 sb_end_write(m->mnt_sb);
3d733633 379 return ret;
8366025e
DH
380}
381EXPORT_SYMBOL_GPL(mnt_want_write);
382
96029c4e 383/**
eb04c282 384 * __mnt_want_write_file - get write access to a file's mount
96029c4e
NP
385 * @file: the file who's mount on which to take a write
386 *
14e43bf4
EB
387 * This is like __mnt_want_write, but if the file is already open for writing it
388 * skips incrementing mnt_writers (since the open file already has a reference)
389 * and instead only does the check for emergency r/o remounts. This must be
390 * paired with __mnt_drop_write_file.
96029c4e 391 */
eb04c282 392int __mnt_want_write_file(struct file *file)
96029c4e 393{
14e43bf4
EB
394 if (file->f_mode & FMODE_WRITER) {
395 /*
396 * Superblock may have become readonly while there are still
397 * writable fd's, e.g. due to a fs error with errors=remount-ro
398 */
399 if (__mnt_is_readonly(file->f_path.mnt))
400 return -EROFS;
401 return 0;
402 }
403 return __mnt_want_write(file->f_path.mnt);
96029c4e 404}
eb04c282 405
7c6893e3
MS
406/**
407 * mnt_want_write_file - get write access to a file's mount
408 * @file: the file who's mount on which to take a write
409 *
14e43bf4
EB
410 * This is like mnt_want_write, but if the file is already open for writing it
411 * skips incrementing mnt_writers (since the open file already has a reference)
412 * and instead only does the freeze protection and the check for emergency r/o
413 * remounts. This must be paired with mnt_drop_write_file.
7c6893e3
MS
414 */
415int mnt_want_write_file(struct file *file)
416{
417 int ret;
418
a6795a58 419 sb_start_write(file_inode(file)->i_sb);
eb04c282
JK
420 ret = __mnt_want_write_file(file);
421 if (ret)
a6795a58 422 sb_end_write(file_inode(file)->i_sb);
7c6893e3
MS
423 return ret;
424}
96029c4e
NP
425EXPORT_SYMBOL_GPL(mnt_want_write_file);
426
8366025e 427/**
eb04c282 428 * __mnt_drop_write - give up write access to a mount
8366025e
DH
429 * @mnt: the mount on which to give up write access
430 *
431 * Tells the low-level filesystem that we are done
432 * performing writes to it. Must be matched with
eb04c282 433 * __mnt_want_write() call above.
8366025e 434 */
eb04c282 435void __mnt_drop_write(struct vfsmount *mnt)
8366025e 436{
d3ef3d73 437 preempt_disable();
83adc753 438 mnt_dec_writers(real_mount(mnt));
d3ef3d73 439 preempt_enable();
8366025e 440}
eb04c282
JK
441
442/**
443 * mnt_drop_write - give up write access to a mount
444 * @mnt: the mount on which to give up write access
445 *
446 * Tells the low-level filesystem that we are done performing writes to it and
447 * also allows filesystem to be frozen again. Must be matched with
448 * mnt_want_write() call above.
449 */
450void mnt_drop_write(struct vfsmount *mnt)
451{
452 __mnt_drop_write(mnt);
453 sb_end_write(mnt->mnt_sb);
454}
8366025e
DH
455EXPORT_SYMBOL_GPL(mnt_drop_write);
456
eb04c282
JK
457void __mnt_drop_write_file(struct file *file)
458{
14e43bf4
EB
459 if (!(file->f_mode & FMODE_WRITER))
460 __mnt_drop_write(file->f_path.mnt);
eb04c282
JK
461}
462
7c6893e3
MS
463void mnt_drop_write_file(struct file *file)
464{
a6795a58 465 __mnt_drop_write_file(file);
7c6893e3
MS
466 sb_end_write(file_inode(file)->i_sb);
467}
2a79f17e
AV
468EXPORT_SYMBOL(mnt_drop_write_file);
469
fbdc2f6c 470static inline int mnt_hold_writers(struct mount *mnt)
8366025e 471{
83adc753 472 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
3d733633 473 /*
d3ef3d73
NP
474 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
475 * should be visible before we do.
3d733633 476 */
d3ef3d73
NP
477 smp_mb();
478
3d733633 479 /*
d3ef3d73
NP
480 * With writers on hold, if this value is zero, then there are
481 * definitely no active writers (although held writers may subsequently
482 * increment the count, they'll have to wait, and decrement it after
483 * seeing MNT_READONLY).
484 *
485 * It is OK to have counter incremented on one CPU and decremented on
486 * another: the sum will add up correctly. The danger would be when we
487 * sum up each counter, if we read a counter before it is incremented,
488 * but then read another CPU's count which it has been subsequently
489 * decremented from -- we would see more decrements than we should.
490 * MNT_WRITE_HOLD protects against this scenario, because
491 * mnt_want_write first increments count, then smp_mb, then spins on
492 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
493 * we're counting up here.
3d733633 494 */
c6653a83 495 if (mnt_get_writers(mnt) > 0)
fbdc2f6c
CB
496 return -EBUSY;
497
498 return 0;
499}
500
501static inline void mnt_unhold_writers(struct mount *mnt)
502{
d3ef3d73
NP
503 /*
504 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
505 * that become unheld will see MNT_READONLY.
506 */
507 smp_wmb();
83adc753 508 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
fbdc2f6c
CB
509}
510
511static int mnt_make_readonly(struct mount *mnt)
512{
513 int ret;
514
515 ret = mnt_hold_writers(mnt);
516 if (!ret)
517 mnt->mnt.mnt_flags |= MNT_READONLY;
518 mnt_unhold_writers(mnt);
3d733633 519 return ret;
8366025e 520}
8366025e 521
4ed5e82f
MS
522int sb_prepare_remount_readonly(struct super_block *sb)
523{
524 struct mount *mnt;
525 int err = 0;
526
8e8b8796
MS
527 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
528 if (atomic_long_read(&sb->s_remove_count))
529 return -EBUSY;
530
719ea2fb 531 lock_mount_hash();
4ed5e82f
MS
532 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
533 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
534 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
535 smp_mb();
536 if (mnt_get_writers(mnt) > 0) {
537 err = -EBUSY;
538 break;
539 }
540 }
541 }
8e8b8796
MS
542 if (!err && atomic_long_read(&sb->s_remove_count))
543 err = -EBUSY;
544
4ed5e82f
MS
545 if (!err) {
546 sb->s_readonly_remount = 1;
547 smp_wmb();
548 }
549 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
550 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
551 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
552 }
719ea2fb 553 unlock_mount_hash();
4ed5e82f
MS
554
555 return err;
556}
557
b105e270 558static void free_vfsmnt(struct mount *mnt)
1da177e4 559{
a6435940
CB
560 struct user_namespace *mnt_userns;
561
562 mnt_userns = mnt_user_ns(&mnt->mnt);
563 if (mnt_userns != &init_user_ns)
564 put_user_ns(mnt_userns);
fcc139ae 565 kfree_const(mnt->mnt_devname);
d3ef3d73 566#ifdef CONFIG_SMP
68e8a9fe 567 free_percpu(mnt->mnt_pcp);
d3ef3d73 568#endif
b105e270 569 kmem_cache_free(mnt_cache, mnt);
1da177e4
LT
570}
571
8ffcb32e
DH
572static void delayed_free_vfsmnt(struct rcu_head *head)
573{
574 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
575}
576
48a066e7 577/* call under rcu_read_lock */
294d71ff 578int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
48a066e7
AV
579{
580 struct mount *mnt;
581 if (read_seqretry(&mount_lock, seq))
294d71ff 582 return 1;
48a066e7 583 if (bastard == NULL)
294d71ff 584 return 0;
48a066e7
AV
585 mnt = real_mount(bastard);
586 mnt_add_count(mnt, 1);
119e1ef8 587 smp_mb(); // see mntput_no_expire()
48a066e7 588 if (likely(!read_seqretry(&mount_lock, seq)))
294d71ff 589 return 0;
48a066e7
AV
590 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
591 mnt_add_count(mnt, -1);
294d71ff
AV
592 return 1;
593 }
119e1ef8
AV
594 lock_mount_hash();
595 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
596 mnt_add_count(mnt, -1);
597 unlock_mount_hash();
598 return 1;
599 }
600 unlock_mount_hash();
601 /* caller will mntput() */
294d71ff
AV
602 return -1;
603}
604
605/* call under rcu_read_lock */
606bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
607{
608 int res = __legitimize_mnt(bastard, seq);
609 if (likely(!res))
610 return true;
611 if (unlikely(res < 0)) {
612 rcu_read_unlock();
613 mntput(bastard);
614 rcu_read_lock();
48a066e7 615 }
48a066e7
AV
616 return false;
617}
618
1da177e4 619/*
474279dc 620 * find the first mount at @dentry on vfsmount @mnt.
48a066e7 621 * call under rcu_read_lock()
1da177e4 622 */
474279dc 623struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
1da177e4 624{
38129a13 625 struct hlist_head *head = m_hash(mnt, dentry);
474279dc
AV
626 struct mount *p;
627
38129a13 628 hlist_for_each_entry_rcu(p, head, mnt_hash)
474279dc
AV
629 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
630 return p;
631 return NULL;
632}
633
a05964f3 634/*
f015f126
DH
635 * lookup_mnt - Return the first child mount mounted at path
636 *
637 * "First" means first mounted chronologically. If you create the
638 * following mounts:
639 *
640 * mount /dev/sda1 /mnt
641 * mount /dev/sda2 /mnt
642 * mount /dev/sda3 /mnt
643 *
644 * Then lookup_mnt() on the base /mnt dentry in the root mount will
645 * return successively the root dentry and vfsmount of /dev/sda1, then
646 * /dev/sda2, then /dev/sda3, then NULL.
647 *
648 * lookup_mnt takes a reference to the found vfsmount.
a05964f3 649 */
ca71cf71 650struct vfsmount *lookup_mnt(const struct path *path)
a05964f3 651{
c7105365 652 struct mount *child_mnt;
48a066e7
AV
653 struct vfsmount *m;
654 unsigned seq;
99b7db7b 655
48a066e7
AV
656 rcu_read_lock();
657 do {
658 seq = read_seqbegin(&mount_lock);
659 child_mnt = __lookup_mnt(path->mnt, path->dentry);
660 m = child_mnt ? &child_mnt->mnt : NULL;
661 } while (!legitimize_mnt(m, seq));
662 rcu_read_unlock();
663 return m;
a05964f3
RP
664}
665
9f6c61f9
MS
666static inline void lock_ns_list(struct mnt_namespace *ns)
667{
668 spin_lock(&ns->ns_lock);
669}
670
671static inline void unlock_ns_list(struct mnt_namespace *ns)
672{
673 spin_unlock(&ns->ns_lock);
674}
675
676static inline bool mnt_is_cursor(struct mount *mnt)
677{
678 return mnt->mnt.mnt_flags & MNT_CURSOR;
679}
680
7af1364f
EB
681/*
682 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
683 * current mount namespace.
684 *
685 * The common case is dentries are not mountpoints at all and that
686 * test is handled inline. For the slow case when we are actually
687 * dealing with a mountpoint of some kind, walk through all of the
688 * mounts in the current mount namespace and test to see if the dentry
689 * is a mountpoint.
690 *
691 * The mount_hashtable is not usable in the context because we
692 * need to identify all mounts that may be in the current mount
693 * namespace not just a mount that happens to have some specified
694 * parent mount.
695 */
696bool __is_local_mountpoint(struct dentry *dentry)
697{
698 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
699 struct mount *mnt;
700 bool is_covered = false;
701
7af1364f 702 down_read(&namespace_sem);
9f6c61f9 703 lock_ns_list(ns);
7af1364f 704 list_for_each_entry(mnt, &ns->list, mnt_list) {
9f6c61f9
MS
705 if (mnt_is_cursor(mnt))
706 continue;
7af1364f
EB
707 is_covered = (mnt->mnt_mountpoint == dentry);
708 if (is_covered)
709 break;
710 }
9f6c61f9 711 unlock_ns_list(ns);
7af1364f 712 up_read(&namespace_sem);
5ad05cc8 713
7af1364f
EB
714 return is_covered;
715}
716
e2dfa935 717static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
84d17192 718{
0818bf27 719 struct hlist_head *chain = mp_hash(dentry);
84d17192
AV
720 struct mountpoint *mp;
721
0818bf27 722 hlist_for_each_entry(mp, chain, m_hash) {
84d17192 723 if (mp->m_dentry == dentry) {
84d17192
AV
724 mp->m_count++;
725 return mp;
726 }
727 }
e2dfa935
EB
728 return NULL;
729}
730
3895dbf8 731static struct mountpoint *get_mountpoint(struct dentry *dentry)
e2dfa935 732{
3895dbf8 733 struct mountpoint *mp, *new = NULL;
e2dfa935 734 int ret;
84d17192 735
3895dbf8 736 if (d_mountpoint(dentry)) {
1e9c75fb
BC
737 /* might be worth a WARN_ON() */
738 if (d_unlinked(dentry))
739 return ERR_PTR(-ENOENT);
3895dbf8
EB
740mountpoint:
741 read_seqlock_excl(&mount_lock);
742 mp = lookup_mountpoint(dentry);
743 read_sequnlock_excl(&mount_lock);
744 if (mp)
745 goto done;
746 }
747
748 if (!new)
749 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
750 if (!new)
84d17192
AV
751 return ERR_PTR(-ENOMEM);
752
3895dbf8
EB
753
754 /* Exactly one processes may set d_mounted */
eed81007 755 ret = d_set_mounted(dentry);
eed81007 756
3895dbf8
EB
757 /* Someone else set d_mounted? */
758 if (ret == -EBUSY)
759 goto mountpoint;
760
761 /* The dentry is not available as a mountpoint? */
762 mp = ERR_PTR(ret);
763 if (ret)
764 goto done;
765
766 /* Add the new mountpoint to the hash table */
767 read_seqlock_excl(&mount_lock);
4edbe133 768 new->m_dentry = dget(dentry);
3895dbf8
EB
769 new->m_count = 1;
770 hlist_add_head(&new->m_hash, mp_hash(dentry));
771 INIT_HLIST_HEAD(&new->m_list);
772 read_sequnlock_excl(&mount_lock);
773
774 mp = new;
775 new = NULL;
776done:
777 kfree(new);
84d17192
AV
778 return mp;
779}
780
4edbe133
AV
781/*
782 * vfsmount lock must be held. Additionally, the caller is responsible
783 * for serializing calls for given disposal list.
784 */
785static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
84d17192
AV
786{
787 if (!--mp->m_count) {
788 struct dentry *dentry = mp->m_dentry;
0a5eb7c8 789 BUG_ON(!hlist_empty(&mp->m_list));
84d17192
AV
790 spin_lock(&dentry->d_lock);
791 dentry->d_flags &= ~DCACHE_MOUNTED;
792 spin_unlock(&dentry->d_lock);
4edbe133 793 dput_to_list(dentry, list);
0818bf27 794 hlist_del(&mp->m_hash);
84d17192
AV
795 kfree(mp);
796 }
797}
798
4edbe133
AV
799/* called with namespace_lock and vfsmount lock */
800static void put_mountpoint(struct mountpoint *mp)
801{
802 __put_mountpoint(mp, &ex_mountpoints);
803}
804
143c8c91 805static inline int check_mnt(struct mount *mnt)
1da177e4 806{
6b3286ed 807 return mnt->mnt_ns == current->nsproxy->mnt_ns;
1da177e4
LT
808}
809
99b7db7b
NP
810/*
811 * vfsmount lock must be held for write
812 */
6b3286ed 813static void touch_mnt_namespace(struct mnt_namespace *ns)
5addc5dd
AV
814{
815 if (ns) {
816 ns->event = ++event;
817 wake_up_interruptible(&ns->poll);
818 }
819}
820
99b7db7b
NP
821/*
822 * vfsmount lock must be held for write
823 */
6b3286ed 824static void __touch_mnt_namespace(struct mnt_namespace *ns)
5addc5dd
AV
825{
826 if (ns && ns->event != event) {
827 ns->event = event;
828 wake_up_interruptible(&ns->poll);
829 }
830}
831
99b7db7b
NP
832/*
833 * vfsmount lock must be held for write
834 */
e4e59906 835static struct mountpoint *unhash_mnt(struct mount *mnt)
419148da 836{
e4e59906 837 struct mountpoint *mp;
0714a533 838 mnt->mnt_parent = mnt;
a73324da 839 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
6b41d536 840 list_del_init(&mnt->mnt_child);
38129a13 841 hlist_del_init_rcu(&mnt->mnt_hash);
0a5eb7c8 842 hlist_del_init(&mnt->mnt_mp_list);
e4e59906 843 mp = mnt->mnt_mp;
84d17192 844 mnt->mnt_mp = NULL;
e4e59906 845 return mp;
7bdb11de
EB
846}
847
6a46c573
EB
848/*
849 * vfsmount lock must be held for write
850 */
851static void umount_mnt(struct mount *mnt)
852{
e4e59906 853 put_mountpoint(unhash_mnt(mnt));
6a46c573
EB
854}
855
99b7db7b
NP
856/*
857 * vfsmount lock must be held for write
858 */
84d17192
AV
859void mnt_set_mountpoint(struct mount *mnt,
860 struct mountpoint *mp,
44d964d6 861 struct mount *child_mnt)
b90fa9ae 862{
84d17192 863 mp->m_count++;
3a2393d7 864 mnt_add_count(mnt, 1); /* essentially, that's mntget */
4edbe133 865 child_mnt->mnt_mountpoint = mp->m_dentry;
3a2393d7 866 child_mnt->mnt_parent = mnt;
84d17192 867 child_mnt->mnt_mp = mp;
0a5eb7c8 868 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
b90fa9ae
RP
869}
870
1064f874
EB
871static void __attach_mnt(struct mount *mnt, struct mount *parent)
872{
873 hlist_add_head_rcu(&mnt->mnt_hash,
874 m_hash(&parent->mnt, mnt->mnt_mountpoint));
875 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
876}
877
99b7db7b
NP
878/*
879 * vfsmount lock must be held for write
880 */
84d17192
AV
881static void attach_mnt(struct mount *mnt,
882 struct mount *parent,
883 struct mountpoint *mp)
1da177e4 884{
84d17192 885 mnt_set_mountpoint(parent, mp, mnt);
1064f874 886 __attach_mnt(mnt, parent);
b90fa9ae
RP
887}
888
1064f874 889void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
12a5b529 890{
1064f874 891 struct mountpoint *old_mp = mnt->mnt_mp;
1064f874
EB
892 struct mount *old_parent = mnt->mnt_parent;
893
894 list_del_init(&mnt->mnt_child);
895 hlist_del_init(&mnt->mnt_mp_list);
896 hlist_del_init_rcu(&mnt->mnt_hash);
897
898 attach_mnt(mnt, parent, mp);
899
900 put_mountpoint(old_mp);
1064f874 901 mnt_add_count(old_parent, -1);
12a5b529
AV
902}
903
b90fa9ae 904/*
99b7db7b 905 * vfsmount lock must be held for write
b90fa9ae 906 */
1064f874 907static void commit_tree(struct mount *mnt)
b90fa9ae 908{
0714a533 909 struct mount *parent = mnt->mnt_parent;
83adc753 910 struct mount *m;
b90fa9ae 911 LIST_HEAD(head);
143c8c91 912 struct mnt_namespace *n = parent->mnt_ns;
b90fa9ae 913
0714a533 914 BUG_ON(parent == mnt);
b90fa9ae 915
1a4eeaf2 916 list_add_tail(&head, &mnt->mnt_list);
f7a99c5b 917 list_for_each_entry(m, &head, mnt_list)
143c8c91 918 m->mnt_ns = n;
f03c6599 919
b90fa9ae
RP
920 list_splice(&head, n->list.prev);
921
d2921684
EB
922 n->mounts += n->pending_mounts;
923 n->pending_mounts = 0;
924
1064f874 925 __attach_mnt(mnt, parent);
6b3286ed 926 touch_mnt_namespace(n);
1da177e4
LT
927}
928
909b0a88 929static struct mount *next_mnt(struct mount *p, struct mount *root)
1da177e4 930{
6b41d536
AV
931 struct list_head *next = p->mnt_mounts.next;
932 if (next == &p->mnt_mounts) {
1da177e4 933 while (1) {
909b0a88 934 if (p == root)
1da177e4 935 return NULL;
6b41d536
AV
936 next = p->mnt_child.next;
937 if (next != &p->mnt_parent->mnt_mounts)
1da177e4 938 break;
0714a533 939 p = p->mnt_parent;
1da177e4
LT
940 }
941 }
6b41d536 942 return list_entry(next, struct mount, mnt_child);
1da177e4
LT
943}
944
315fc83e 945static struct mount *skip_mnt_tree(struct mount *p)
9676f0c6 946{
6b41d536
AV
947 struct list_head *prev = p->mnt_mounts.prev;
948 while (prev != &p->mnt_mounts) {
949 p = list_entry(prev, struct mount, mnt_child);
950 prev = p->mnt_mounts.prev;
9676f0c6
RP
951 }
952 return p;
953}
954
8f291889
AV
955/**
956 * vfs_create_mount - Create a mount for a configured superblock
957 * @fc: The configuration context with the superblock attached
958 *
959 * Create a mount to an already configured superblock. If necessary, the
960 * caller should invoke vfs_get_tree() before calling this.
961 *
962 * Note that this does not attach the mount to anything.
963 */
964struct vfsmount *vfs_create_mount(struct fs_context *fc)
9d412a43 965{
b105e270 966 struct mount *mnt;
9d412a43 967
8f291889
AV
968 if (!fc->root)
969 return ERR_PTR(-EINVAL);
9d412a43 970
8f291889 971 mnt = alloc_vfsmnt(fc->source ?: "none");
9d412a43
AV
972 if (!mnt)
973 return ERR_PTR(-ENOMEM);
974
8f291889 975 if (fc->sb_flags & SB_KERNMOUNT)
b105e270 976 mnt->mnt.mnt_flags = MNT_INTERNAL;
9d412a43 977
8f291889
AV
978 atomic_inc(&fc->root->d_sb->s_active);
979 mnt->mnt.mnt_sb = fc->root->d_sb;
980 mnt->mnt.mnt_root = dget(fc->root);
981 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
982 mnt->mnt_parent = mnt;
9d412a43 983
719ea2fb 984 lock_mount_hash();
8f291889 985 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
719ea2fb 986 unlock_mount_hash();
b105e270 987 return &mnt->mnt;
9d412a43 988}
8f291889
AV
989EXPORT_SYMBOL(vfs_create_mount);
990
991struct vfsmount *fc_mount(struct fs_context *fc)
992{
993 int err = vfs_get_tree(fc);
994 if (!err) {
995 up_write(&fc->root->d_sb->s_umount);
996 return vfs_create_mount(fc);
997 }
998 return ERR_PTR(err);
999}
1000EXPORT_SYMBOL(fc_mount);
1001
9bc61ab1
DH
1002struct vfsmount *vfs_kern_mount(struct file_system_type *type,
1003 int flags, const char *name,
1004 void *data)
9d412a43 1005{
9bc61ab1 1006 struct fs_context *fc;
8f291889 1007 struct vfsmount *mnt;
9bc61ab1 1008 int ret = 0;
9d412a43
AV
1009
1010 if (!type)
3e1aeb00 1011 return ERR_PTR(-EINVAL);
9d412a43 1012
9bc61ab1
DH
1013 fc = fs_context_for_mount(type, flags);
1014 if (IS_ERR(fc))
1015 return ERR_CAST(fc);
1016
3e1aeb00
DH
1017 if (name)
1018 ret = vfs_parse_fs_string(fc, "source",
1019 name, strlen(name));
9bc61ab1
DH
1020 if (!ret)
1021 ret = parse_monolithic_mount_data(fc, data);
1022 if (!ret)
8f291889
AV
1023 mnt = fc_mount(fc);
1024 else
1025 mnt = ERR_PTR(ret);
9d412a43 1026
9bc61ab1 1027 put_fs_context(fc);
8f291889 1028 return mnt;
9d412a43
AV
1029}
1030EXPORT_SYMBOL_GPL(vfs_kern_mount);
1031
93faccbb
EB
1032struct vfsmount *
1033vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1034 const char *name, void *data)
1035{
1036 /* Until it is worked out how to pass the user namespace
1037 * through from the parent mount to the submount don't support
1038 * unprivileged mounts with submounts.
1039 */
1040 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1041 return ERR_PTR(-EPERM);
1042
e462ec50 1043 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
93faccbb
EB
1044}
1045EXPORT_SYMBOL_GPL(vfs_submount);
1046
87129cc0 1047static struct mount *clone_mnt(struct mount *old, struct dentry *root,
36341f64 1048 int flag)
1da177e4 1049{
87129cc0 1050 struct super_block *sb = old->mnt.mnt_sb;
be34d1a3
DH
1051 struct mount *mnt;
1052 int err;
1da177e4 1053
be34d1a3
DH
1054 mnt = alloc_vfsmnt(old->mnt_devname);
1055 if (!mnt)
1056 return ERR_PTR(-ENOMEM);
719f5d7f 1057
7a472ef4 1058 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
be34d1a3
DH
1059 mnt->mnt_group_id = 0; /* not a peer of original */
1060 else
1061 mnt->mnt_group_id = old->mnt_group_id;
b90fa9ae 1062
be34d1a3
DH
1063 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1064 err = mnt_alloc_group_id(mnt);
1065 if (err)
1066 goto out_free;
1da177e4 1067 }
be34d1a3 1068
16a34adb
AV
1069 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1070 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
5ff9d8a6 1071
be34d1a3 1072 atomic_inc(&sb->s_active);
a6435940
CB
1073 mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt);
1074 if (mnt->mnt.mnt_userns != &init_user_ns)
1075 mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns);
be34d1a3
DH
1076 mnt->mnt.mnt_sb = sb;
1077 mnt->mnt.mnt_root = dget(root);
1078 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1079 mnt->mnt_parent = mnt;
719ea2fb 1080 lock_mount_hash();
be34d1a3 1081 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
719ea2fb 1082 unlock_mount_hash();
be34d1a3 1083
7a472ef4
EB
1084 if ((flag & CL_SLAVE) ||
1085 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
be34d1a3
DH
1086 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1087 mnt->mnt_master = old;
1088 CLEAR_MNT_SHARED(mnt);
1089 } else if (!(flag & CL_PRIVATE)) {
1090 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1091 list_add(&mnt->mnt_share, &old->mnt_share);
1092 if (IS_MNT_SLAVE(old))
1093 list_add(&mnt->mnt_slave, &old->mnt_slave);
1094 mnt->mnt_master = old->mnt_master;
5235d448
AV
1095 } else {
1096 CLEAR_MNT_SHARED(mnt);
be34d1a3
DH
1097 }
1098 if (flag & CL_MAKE_SHARED)
1099 set_mnt_shared(mnt);
1100
1101 /* stick the duplicate mount on the same expiry list
1102 * as the original if that was on one */
1103 if (flag & CL_EXPIRE) {
1104 if (!list_empty(&old->mnt_expire))
1105 list_add(&mnt->mnt_expire, &old->mnt_expire);
1106 }
1107
cb338d06 1108 return mnt;
719f5d7f
MS
1109
1110 out_free:
8ffcb32e 1111 mnt_free_id(mnt);
719f5d7f 1112 free_vfsmnt(mnt);
be34d1a3 1113 return ERR_PTR(err);
1da177e4
LT
1114}
1115
9ea459e1
AV
1116static void cleanup_mnt(struct mount *mnt)
1117{
56cbb429
AV
1118 struct hlist_node *p;
1119 struct mount *m;
9ea459e1 1120 /*
56cbb429
AV
1121 * The warning here probably indicates that somebody messed
1122 * up a mnt_want/drop_write() pair. If this happens, the
1123 * filesystem was probably unable to make r/w->r/o transitions.
9ea459e1
AV
1124 * The locking used to deal with mnt_count decrement provides barriers,
1125 * so mnt_get_writers() below is safe.
1126 */
1127 WARN_ON(mnt_get_writers(mnt));
1128 if (unlikely(mnt->mnt_pins.first))
1129 mnt_pin_kill(mnt);
56cbb429
AV
1130 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1131 hlist_del(&m->mnt_umount);
1132 mntput(&m->mnt);
1133 }
9ea459e1
AV
1134 fsnotify_vfsmount_delete(&mnt->mnt);
1135 dput(mnt->mnt.mnt_root);
1136 deactivate_super(mnt->mnt.mnt_sb);
1137 mnt_free_id(mnt);
1138 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1139}
1140
1141static void __cleanup_mnt(struct rcu_head *head)
1142{
1143 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1144}
1145
1146static LLIST_HEAD(delayed_mntput_list);
1147static void delayed_mntput(struct work_struct *unused)
1148{
1149 struct llist_node *node = llist_del_all(&delayed_mntput_list);
29785735 1150 struct mount *m, *t;
9ea459e1 1151
29785735
BP
1152 llist_for_each_entry_safe(m, t, node, mnt_llist)
1153 cleanup_mnt(m);
9ea459e1
AV
1154}
1155static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1156
900148dc 1157static void mntput_no_expire(struct mount *mnt)
b3e19d92 1158{
4edbe133 1159 LIST_HEAD(list);
edf7ddbf 1160 int count;
4edbe133 1161
48a066e7 1162 rcu_read_lock();
9ea0a46c
AV
1163 if (likely(READ_ONCE(mnt->mnt_ns))) {
1164 /*
1165 * Since we don't do lock_mount_hash() here,
1166 * ->mnt_ns can change under us. However, if it's
1167 * non-NULL, then there's a reference that won't
1168 * be dropped until after an RCU delay done after
1169 * turning ->mnt_ns NULL. So if we observe it
1170 * non-NULL under rcu_read_lock(), the reference
1171 * we are dropping is not the final one.
1172 */
1173 mnt_add_count(mnt, -1);
48a066e7 1174 rcu_read_unlock();
f03c6599 1175 return;
b3e19d92 1176 }
719ea2fb 1177 lock_mount_hash();
119e1ef8
AV
1178 /*
1179 * make sure that if __legitimize_mnt() has not seen us grab
1180 * mount_lock, we'll see their refcount increment here.
1181 */
1182 smp_mb();
9ea0a46c 1183 mnt_add_count(mnt, -1);
edf7ddbf
EB
1184 count = mnt_get_count(mnt);
1185 if (count != 0) {
1186 WARN_ON(count < 0);
48a066e7 1187 rcu_read_unlock();
719ea2fb 1188 unlock_mount_hash();
99b7db7b
NP
1189 return;
1190 }
48a066e7
AV
1191 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1192 rcu_read_unlock();
1193 unlock_mount_hash();
1194 return;
1195 }
1196 mnt->mnt.mnt_flags |= MNT_DOOMED;
1197 rcu_read_unlock();
962830df 1198
39f7c4db 1199 list_del(&mnt->mnt_instance);
ce07d891
EB
1200
1201 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1202 struct mount *p, *tmp;
1203 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
4edbe133 1204 __put_mountpoint(unhash_mnt(p), &list);
56cbb429 1205 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
ce07d891
EB
1206 }
1207 }
719ea2fb 1208 unlock_mount_hash();
4edbe133 1209 shrink_dentry_list(&list);
649a795a 1210
9ea459e1
AV
1211 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1212 struct task_struct *task = current;
1213 if (likely(!(task->flags & PF_KTHREAD))) {
1214 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
91989c70 1215 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
9ea459e1
AV
1216 return;
1217 }
1218 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1219 schedule_delayed_work(&delayed_mntput_work, 1);
1220 return;
1221 }
1222 cleanup_mnt(mnt);
b3e19d92 1223}
b3e19d92
NP
1224
1225void mntput(struct vfsmount *mnt)
1226{
1227 if (mnt) {
863d684f 1228 struct mount *m = real_mount(mnt);
b3e19d92 1229 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
863d684f
AV
1230 if (unlikely(m->mnt_expiry_mark))
1231 m->mnt_expiry_mark = 0;
1232 mntput_no_expire(m);
b3e19d92
NP
1233 }
1234}
1235EXPORT_SYMBOL(mntput);
1236
1237struct vfsmount *mntget(struct vfsmount *mnt)
1238{
1239 if (mnt)
83adc753 1240 mnt_add_count(real_mount(mnt), 1);
b3e19d92
NP
1241 return mnt;
1242}
1243EXPORT_SYMBOL(mntget);
1244
1f287bc4
RD
1245/**
1246 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1247 * @path: path to check
c6609c0a
IK
1248 *
1249 * d_mountpoint() can only be used reliably to establish if a dentry is
1250 * not mounted in any namespace and that common case is handled inline.
1251 * d_mountpoint() isn't aware of the possibility there may be multiple
1252 * mounts using a given dentry in a different namespace. This function
1253 * checks if the passed in path is a mountpoint rather than the dentry
1254 * alone.
1255 */
1256bool path_is_mountpoint(const struct path *path)
1257{
1258 unsigned seq;
1259 bool res;
1260
1261 if (!d_mountpoint(path->dentry))
1262 return false;
1263
1264 rcu_read_lock();
1265 do {
1266 seq = read_seqbegin(&mount_lock);
1267 res = __path_is_mountpoint(path);
1268 } while (read_seqretry(&mount_lock, seq));
1269 rcu_read_unlock();
1270
1271 return res;
1272}
1273EXPORT_SYMBOL(path_is_mountpoint);
1274
ca71cf71 1275struct vfsmount *mnt_clone_internal(const struct path *path)
7b7b1ace 1276{
3064c356
AV
1277 struct mount *p;
1278 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1279 if (IS_ERR(p))
1280 return ERR_CAST(p);
1281 p->mnt.mnt_flags |= MNT_INTERNAL;
1282 return &p->mnt;
7b7b1ace 1283}
1da177e4 1284
a1a2c409 1285#ifdef CONFIG_PROC_FS
9f6c61f9
MS
1286static struct mount *mnt_list_next(struct mnt_namespace *ns,
1287 struct list_head *p)
1288{
1289 struct mount *mnt, *ret = NULL;
1290
1291 lock_ns_list(ns);
1292 list_for_each_continue(p, &ns->list) {
1293 mnt = list_entry(p, typeof(*mnt), mnt_list);
1294 if (!mnt_is_cursor(mnt)) {
1295 ret = mnt;
1296 break;
1297 }
1298 }
1299 unlock_ns_list(ns);
1300
1301 return ret;
1302}
1303
0226f492 1304/* iterator; we want it to have access to namespace_sem, thus here... */
1da177e4
LT
1305static void *m_start(struct seq_file *m, loff_t *pos)
1306{
ede1bf0d 1307 struct proc_mounts *p = m->private;
9f6c61f9 1308 struct list_head *prev;
1da177e4 1309
390c6843 1310 down_read(&namespace_sem);
9f6c61f9
MS
1311 if (!*pos) {
1312 prev = &p->ns->list;
1313 } else {
1314 prev = &p->cursor.mnt_list;
1315
1316 /* Read after we'd reached the end? */
1317 if (list_empty(prev))
1318 return NULL;
c7999c36
AV
1319 }
1320
9f6c61f9 1321 return mnt_list_next(p->ns, prev);
1da177e4
LT
1322}
1323
1324static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1325{
ede1bf0d 1326 struct proc_mounts *p = m->private;
9f6c61f9 1327 struct mount *mnt = v;
b0765fb8 1328
9f6c61f9
MS
1329 ++*pos;
1330 return mnt_list_next(p->ns, &mnt->mnt_list);
1da177e4
LT
1331}
1332
1333static void m_stop(struct seq_file *m, void *v)
1334{
9f6c61f9
MS
1335 struct proc_mounts *p = m->private;
1336 struct mount *mnt = v;
1337
1338 lock_ns_list(p->ns);
1339 if (mnt)
1340 list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
1341 else
1342 list_del_init(&p->cursor.mnt_list);
1343 unlock_ns_list(p->ns);
390c6843 1344 up_read(&namespace_sem);
1da177e4
LT
1345}
1346
0226f492 1347static int m_show(struct seq_file *m, void *v)
2d4d4864 1348{
ede1bf0d 1349 struct proc_mounts *p = m->private;
9f6c61f9 1350 struct mount *r = v;
0226f492 1351 return p->show(m, &r->mnt);
1da177e4
LT
1352}
1353
a1a2c409 1354const struct seq_operations mounts_op = {
1da177e4
LT
1355 .start = m_start,
1356 .next = m_next,
1357 .stop = m_stop,
0226f492 1358 .show = m_show,
b4629fe2 1359};
9f6c61f9
MS
1360
1361void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
1362{
1363 down_read(&namespace_sem);
1364 lock_ns_list(ns);
1365 list_del(&cursor->mnt_list);
1366 unlock_ns_list(ns);
1367 up_read(&namespace_sem);
1368}
a1a2c409 1369#endif /* CONFIG_PROC_FS */
b4629fe2 1370
1da177e4
LT
1371/**
1372 * may_umount_tree - check if a mount tree is busy
1f287bc4 1373 * @m: root of mount tree
1da177e4
LT
1374 *
1375 * This is called to check if a tree of mounts has any
1376 * open files, pwds, chroots or sub mounts that are
1377 * busy.
1378 */
909b0a88 1379int may_umount_tree(struct vfsmount *m)
1da177e4 1380{
909b0a88 1381 struct mount *mnt = real_mount(m);
36341f64
RP
1382 int actual_refs = 0;
1383 int minimum_refs = 0;
315fc83e 1384 struct mount *p;
909b0a88 1385 BUG_ON(!m);
1da177e4 1386
b3e19d92 1387 /* write lock needed for mnt_get_count */
719ea2fb 1388 lock_mount_hash();
909b0a88 1389 for (p = mnt; p; p = next_mnt(p, mnt)) {
83adc753 1390 actual_refs += mnt_get_count(p);
1da177e4 1391 minimum_refs += 2;
1da177e4 1392 }
719ea2fb 1393 unlock_mount_hash();
1da177e4
LT
1394
1395 if (actual_refs > minimum_refs)
e3474a8e 1396 return 0;
1da177e4 1397
e3474a8e 1398 return 1;
1da177e4
LT
1399}
1400
1401EXPORT_SYMBOL(may_umount_tree);
1402
1403/**
1404 * may_umount - check if a mount point is busy
1405 * @mnt: root of mount
1406 *
1407 * This is called to check if a mount point has any
1408 * open files, pwds, chroots or sub mounts. If the
1409 * mount has sub mounts this will return busy
1410 * regardless of whether the sub mounts are busy.
1411 *
1412 * Doesn't take quota and stuff into account. IOW, in some cases it will
1413 * give false negatives. The main reason why it's here is that we need
1414 * a non-destructive way to look for easily umountable filesystems.
1415 */
1416int may_umount(struct vfsmount *mnt)
1417{
e3474a8e 1418 int ret = 1;
8ad08d8a 1419 down_read(&namespace_sem);
719ea2fb 1420 lock_mount_hash();
1ab59738 1421 if (propagate_mount_busy(real_mount(mnt), 2))
e3474a8e 1422 ret = 0;
719ea2fb 1423 unlock_mount_hash();
8ad08d8a 1424 up_read(&namespace_sem);
a05964f3 1425 return ret;
1da177e4
LT
1426}
1427
1428EXPORT_SYMBOL(may_umount);
1429
97216be0 1430static void namespace_unlock(void)
70fbcdf4 1431{
a3b3c562 1432 struct hlist_head head;
56cbb429
AV
1433 struct hlist_node *p;
1434 struct mount *m;
4edbe133 1435 LIST_HEAD(list);
97216be0 1436
a3b3c562 1437 hlist_move_list(&unmounted, &head);
4edbe133 1438 list_splice_init(&ex_mountpoints, &list);
97216be0 1439
97216be0
AV
1440 up_write(&namespace_sem);
1441
4edbe133
AV
1442 shrink_dentry_list(&list);
1443
a3b3c562
EB
1444 if (likely(hlist_empty(&head)))
1445 return;
1446
22cb7405 1447 synchronize_rcu_expedited();
48a066e7 1448
56cbb429
AV
1449 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1450 hlist_del(&m->mnt_umount);
1451 mntput(&m->mnt);
1452 }
70fbcdf4
RP
1453}
1454
97216be0 1455static inline void namespace_lock(void)
e3197d83 1456{
97216be0 1457 down_write(&namespace_sem);
e3197d83
AV
1458}
1459
e819f152
EB
1460enum umount_tree_flags {
1461 UMOUNT_SYNC = 1,
1462 UMOUNT_PROPAGATE = 2,
e0c9c0af 1463 UMOUNT_CONNECTED = 4,
e819f152 1464};
f2d0a123
EB
1465
1466static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1467{
1468 /* Leaving mounts connected is only valid for lazy umounts */
1469 if (how & UMOUNT_SYNC)
1470 return true;
1471
1472 /* A mount without a parent has nothing to be connected to */
1473 if (!mnt_has_parent(mnt))
1474 return true;
1475
1476 /* Because the reference counting rules change when mounts are
1477 * unmounted and connected, umounted mounts may not be
1478 * connected to mounted mounts.
1479 */
1480 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1481 return true;
1482
1483 /* Has it been requested that the mount remain connected? */
1484 if (how & UMOUNT_CONNECTED)
1485 return false;
1486
1487 /* Is the mount locked such that it needs to remain connected? */
1488 if (IS_MNT_LOCKED(mnt))
1489 return false;
1490
1491 /* By default disconnect the mount */
1492 return true;
1493}
1494
99b7db7b 1495/*
48a066e7 1496 * mount_lock must be held
99b7db7b
NP
1497 * namespace_sem must be held for write
1498 */
e819f152 1499static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1da177e4 1500{
c003b26f 1501 LIST_HEAD(tmp_list);
315fc83e 1502 struct mount *p;
1da177e4 1503
5d88457e
EB
1504 if (how & UMOUNT_PROPAGATE)
1505 propagate_mount_unlock(mnt);
1506
c003b26f 1507 /* Gather the mounts to umount */
590ce4bc
EB
1508 for (p = mnt; p; p = next_mnt(p, mnt)) {
1509 p->mnt.mnt_flags |= MNT_UMOUNT;
c003b26f 1510 list_move(&p->mnt_list, &tmp_list);
590ce4bc 1511 }
1da177e4 1512
411a938b 1513 /* Hide the mounts from mnt_mounts */
c003b26f 1514 list_for_each_entry(p, &tmp_list, mnt_list) {
88b368f2 1515 list_del_init(&p->mnt_child);
c003b26f 1516 }
88b368f2 1517
c003b26f 1518 /* Add propogated mounts to the tmp_list */
e819f152 1519 if (how & UMOUNT_PROPAGATE)
7b8a53fd 1520 propagate_umount(&tmp_list);
a05964f3 1521
c003b26f 1522 while (!list_empty(&tmp_list)) {
d2921684 1523 struct mnt_namespace *ns;
ce07d891 1524 bool disconnect;
c003b26f 1525 p = list_first_entry(&tmp_list, struct mount, mnt_list);
6776db3d 1526 list_del_init(&p->mnt_expire);
1a4eeaf2 1527 list_del_init(&p->mnt_list);
d2921684
EB
1528 ns = p->mnt_ns;
1529 if (ns) {
1530 ns->mounts--;
1531 __touch_mnt_namespace(ns);
1532 }
143c8c91 1533 p->mnt_ns = NULL;
e819f152 1534 if (how & UMOUNT_SYNC)
48a066e7 1535 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
87b95ce0 1536
f2d0a123 1537 disconnect = disconnect_mount(p, how);
676da58d 1538 if (mnt_has_parent(p)) {
81b6b061 1539 mnt_add_count(p->mnt_parent, -1);
ce07d891
EB
1540 if (!disconnect) {
1541 /* Don't forget about p */
1542 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1543 } else {
1544 umount_mnt(p);
1545 }
7c4b93d8 1546 }
0f0afb1d 1547 change_mnt_propagation(p, MS_PRIVATE);
19a1c409
AV
1548 if (disconnect)
1549 hlist_add_head(&p->mnt_umount, &unmounted);
1da177e4
LT
1550 }
1551}
1552
b54b9be7 1553static void shrink_submounts(struct mount *mnt);
c35038be 1554
8d0347f6
DH
1555static int do_umount_root(struct super_block *sb)
1556{
1557 int ret = 0;
1558
1559 down_write(&sb->s_umount);
1560 if (!sb_rdonly(sb)) {
1561 struct fs_context *fc;
1562
1563 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1564 SB_RDONLY);
1565 if (IS_ERR(fc)) {
1566 ret = PTR_ERR(fc);
1567 } else {
1568 ret = parse_monolithic_mount_data(fc, NULL);
1569 if (!ret)
1570 ret = reconfigure_super(fc);
1571 put_fs_context(fc);
1572 }
1573 }
1574 up_write(&sb->s_umount);
1575 return ret;
1576}
1577
1ab59738 1578static int do_umount(struct mount *mnt, int flags)
1da177e4 1579{
1ab59738 1580 struct super_block *sb = mnt->mnt.mnt_sb;
1da177e4
LT
1581 int retval;
1582
1ab59738 1583 retval = security_sb_umount(&mnt->mnt, flags);
1da177e4
LT
1584 if (retval)
1585 return retval;
1586
1587 /*
1588 * Allow userspace to request a mountpoint be expired rather than
1589 * unmounting unconditionally. Unmount only happens if:
1590 * (1) the mark is already set (the mark is cleared by mntput())
1591 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1592 */
1593 if (flags & MNT_EXPIRE) {
1ab59738 1594 if (&mnt->mnt == current->fs->root.mnt ||
1da177e4
LT
1595 flags & (MNT_FORCE | MNT_DETACH))
1596 return -EINVAL;
1597
b3e19d92
NP
1598 /*
1599 * probably don't strictly need the lock here if we examined
1600 * all race cases, but it's a slowpath.
1601 */
719ea2fb 1602 lock_mount_hash();
83adc753 1603 if (mnt_get_count(mnt) != 2) {
719ea2fb 1604 unlock_mount_hash();
1da177e4 1605 return -EBUSY;
b3e19d92 1606 }
719ea2fb 1607 unlock_mount_hash();
1da177e4 1608
863d684f 1609 if (!xchg(&mnt->mnt_expiry_mark, 1))
1da177e4
LT
1610 return -EAGAIN;
1611 }
1612
1613 /*
1614 * If we may have to abort operations to get out of this
1615 * mount, and they will themselves hold resources we must
1616 * allow the fs to do things. In the Unix tradition of
1617 * 'Gee thats tricky lets do it in userspace' the umount_begin
1618 * might fail to complete on the first run through as other tasks
1619 * must return, and the like. Thats for the mount program to worry
1620 * about for the moment.
1621 */
1622
42faad99 1623 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
42faad99 1624 sb->s_op->umount_begin(sb);
42faad99 1625 }
1da177e4
LT
1626
1627 /*
1628 * No sense to grab the lock for this test, but test itself looks
1629 * somewhat bogus. Suggestions for better replacement?
1630 * Ho-hum... In principle, we might treat that as umount + switch
1631 * to rootfs. GC would eventually take care of the old vfsmount.
1632 * Actually it makes sense, especially if rootfs would contain a
1633 * /reboot - static binary that would close all descriptors and
1634 * call reboot(9). Then init(8) could umount root and exec /reboot.
1635 */
1ab59738 1636 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1da177e4
LT
1637 /*
1638 * Special case for "unmounting" root ...
1639 * we just try to remount it readonly.
1640 */
bc6155d1 1641 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
a1480dcc 1642 return -EPERM;
8d0347f6 1643 return do_umount_root(sb);
1da177e4
LT
1644 }
1645
97216be0 1646 namespace_lock();
719ea2fb 1647 lock_mount_hash();
1da177e4 1648
25d202ed
EB
1649 /* Recheck MNT_LOCKED with the locks held */
1650 retval = -EINVAL;
1651 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1652 goto out;
1653
1654 event++;
48a066e7 1655 if (flags & MNT_DETACH) {
1a4eeaf2 1656 if (!list_empty(&mnt->mnt_list))
e819f152 1657 umount_tree(mnt, UMOUNT_PROPAGATE);
1da177e4 1658 retval = 0;
48a066e7
AV
1659 } else {
1660 shrink_submounts(mnt);
1661 retval = -EBUSY;
1662 if (!propagate_mount_busy(mnt, 2)) {
1663 if (!list_empty(&mnt->mnt_list))
e819f152 1664 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
48a066e7
AV
1665 retval = 0;
1666 }
1da177e4 1667 }
25d202ed 1668out:
719ea2fb 1669 unlock_mount_hash();
e3197d83 1670 namespace_unlock();
1da177e4
LT
1671 return retval;
1672}
1673
80b5dce8
EB
1674/*
1675 * __detach_mounts - lazily unmount all mounts on the specified dentry
1676 *
1677 * During unlink, rmdir, and d_drop it is possible to loose the path
1678 * to an existing mountpoint, and wind up leaking the mount.
1679 * detach_mounts allows lazily unmounting those mounts instead of
1680 * leaking them.
1681 *
1682 * The caller may hold dentry->d_inode->i_mutex.
1683 */
1684void __detach_mounts(struct dentry *dentry)
1685{
1686 struct mountpoint *mp;
1687 struct mount *mnt;
1688
1689 namespace_lock();
3895dbf8 1690 lock_mount_hash();
80b5dce8 1691 mp = lookup_mountpoint(dentry);
adc9b5c0 1692 if (!mp)
80b5dce8
EB
1693 goto out_unlock;
1694
e06b933e 1695 event++;
80b5dce8
EB
1696 while (!hlist_empty(&mp->m_list)) {
1697 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
ce07d891 1698 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
fe78fcc8 1699 umount_mnt(mnt);
56cbb429 1700 hlist_add_head(&mnt->mnt_umount, &unmounted);
ce07d891 1701 }
e0c9c0af 1702 else umount_tree(mnt, UMOUNT_CONNECTED);
80b5dce8 1703 }
80b5dce8
EB
1704 put_mountpoint(mp);
1705out_unlock:
3895dbf8 1706 unlock_mount_hash();
80b5dce8
EB
1707 namespace_unlock();
1708}
1709
dd111b31 1710/*
9b40bc90
AV
1711 * Is the caller allowed to modify his namespace?
1712 */
1713static inline bool may_mount(void)
1714{
1715 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1716}
1717
df2474a2 1718#ifdef CONFIG_MANDATORY_FILE_LOCKING
9e8925b6
JL
1719static inline bool may_mandlock(void)
1720{
95ace754 1721 return capable(CAP_SYS_ADMIN);
9e8925b6 1722}
df2474a2
JL
1723#else
1724static inline bool may_mandlock(void)
1725{
1726 pr_warn("VFS: \"mand\" mount option not supported");
1727 return false;
1728}
1729#endif
9e8925b6 1730
25ccd24f 1731static int can_umount(const struct path *path, int flags)
1da177e4 1732{
25ccd24f 1733 struct mount *mnt = real_mount(path->mnt);
1da177e4 1734
9b40bc90
AV
1735 if (!may_mount())
1736 return -EPERM;
41525f56 1737 if (path->dentry != path->mnt->mnt_root)
25ccd24f 1738 return -EINVAL;
143c8c91 1739 if (!check_mnt(mnt))
25ccd24f 1740 return -EINVAL;
25d202ed 1741 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
25ccd24f 1742 return -EINVAL;
b2f5d4dc 1743 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
25ccd24f
CH
1744 return -EPERM;
1745 return 0;
1746}
1747
a0a6df9a 1748// caller is responsible for flags being sane
25ccd24f
CH
1749int path_umount(struct path *path, int flags)
1750{
1751 struct mount *mnt = real_mount(path->mnt);
1752 int ret;
1753
1754 ret = can_umount(path, flags);
1755 if (!ret)
1756 ret = do_umount(mnt, flags);
1da177e4 1757
429731b1 1758 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
41525f56 1759 dput(path->dentry);
900148dc 1760 mntput_no_expire(mnt);
25ccd24f 1761 return ret;
1da177e4
LT
1762}
1763
09267def 1764static int ksys_umount(char __user *name, int flags)
41525f56
CH
1765{
1766 int lookup_flags = LOOKUP_MOUNTPOINT;
1767 struct path path;
1768 int ret;
1769
a0a6df9a
AV
1770 // basic validity checks done first
1771 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1772 return -EINVAL;
1773
41525f56
CH
1774 if (!(flags & UMOUNT_NOFOLLOW))
1775 lookup_flags |= LOOKUP_FOLLOW;
1776 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1777 if (ret)
1778 return ret;
1779 return path_umount(&path, flags);
1780}
1781
3a18ef5c
DB
1782SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1783{
1784 return ksys_umount(name, flags);
1785}
1786
1da177e4
LT
1787#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1788
1789/*
b58fed8b 1790 * The 2.0 compatible umount. No flags.
1da177e4 1791 */
bdc480e3 1792SYSCALL_DEFINE1(oldumount, char __user *, name)
1da177e4 1793{
3a18ef5c 1794 return ksys_umount(name, 0);
1da177e4
LT
1795}
1796
1797#endif
1798
4ce5d2b1 1799static bool is_mnt_ns_file(struct dentry *dentry)
8823c079 1800{
4ce5d2b1 1801 /* Is this a proxy for a mount namespace? */
e149ed2b
AV
1802 return dentry->d_op == &ns_dentry_operations &&
1803 dentry->d_fsdata == &mntns_operations;
4ce5d2b1
EB
1804}
1805
213921f9 1806static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
58be2825
AV
1807{
1808 return container_of(ns, struct mnt_namespace, ns);
1809}
1810
303cc571
CB
1811struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1812{
1813 return &mnt->ns;
1814}
1815
4ce5d2b1
EB
1816static bool mnt_ns_loop(struct dentry *dentry)
1817{
1818 /* Could bind mounting the mount namespace inode cause a
1819 * mount namespace loop?
1820 */
1821 struct mnt_namespace *mnt_ns;
1822 if (!is_mnt_ns_file(dentry))
1823 return false;
1824
f77c8014 1825 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
8823c079
EB
1826 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1827}
1828
87129cc0 1829struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
36341f64 1830 int flag)
1da177e4 1831{
84d17192 1832 struct mount *res, *p, *q, *r, *parent;
1da177e4 1833
4ce5d2b1
EB
1834 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1835 return ERR_PTR(-EINVAL);
1836
1837 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
be34d1a3 1838 return ERR_PTR(-EINVAL);
9676f0c6 1839
36341f64 1840 res = q = clone_mnt(mnt, dentry, flag);
be34d1a3
DH
1841 if (IS_ERR(q))
1842 return q;
1843
a73324da 1844 q->mnt_mountpoint = mnt->mnt_mountpoint;
1da177e4
LT
1845
1846 p = mnt;
6b41d536 1847 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
315fc83e 1848 struct mount *s;
7ec02ef1 1849 if (!is_subdir(r->mnt_mountpoint, dentry))
1da177e4
LT
1850 continue;
1851
909b0a88 1852 for (s = r; s; s = next_mnt(s, r)) {
4ce5d2b1
EB
1853 if (!(flag & CL_COPY_UNBINDABLE) &&
1854 IS_MNT_UNBINDABLE(s)) {
df7342b2
EB
1855 if (s->mnt.mnt_flags & MNT_LOCKED) {
1856 /* Both unbindable and locked. */
1857 q = ERR_PTR(-EPERM);
1858 goto out;
1859 } else {
1860 s = skip_mnt_tree(s);
1861 continue;
1862 }
4ce5d2b1
EB
1863 }
1864 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1865 is_mnt_ns_file(s->mnt.mnt_root)) {
9676f0c6
RP
1866 s = skip_mnt_tree(s);
1867 continue;
1868 }
0714a533
AV
1869 while (p != s->mnt_parent) {
1870 p = p->mnt_parent;
1871 q = q->mnt_parent;
1da177e4 1872 }
87129cc0 1873 p = s;
84d17192 1874 parent = q;
87129cc0 1875 q = clone_mnt(p, p->mnt.mnt_root, flag);
be34d1a3
DH
1876 if (IS_ERR(q))
1877 goto out;
719ea2fb 1878 lock_mount_hash();
1a4eeaf2 1879 list_add_tail(&q->mnt_list, &res->mnt_list);
1064f874 1880 attach_mnt(q, parent, p->mnt_mp);
719ea2fb 1881 unlock_mount_hash();
1da177e4
LT
1882 }
1883 }
1884 return res;
be34d1a3 1885out:
1da177e4 1886 if (res) {
719ea2fb 1887 lock_mount_hash();
e819f152 1888 umount_tree(res, UMOUNT_SYNC);
719ea2fb 1889 unlock_mount_hash();
1da177e4 1890 }
be34d1a3 1891 return q;
1da177e4
LT
1892}
1893
be34d1a3
DH
1894/* Caller should check returned pointer for errors */
1895
ca71cf71 1896struct vfsmount *collect_mounts(const struct path *path)
8aec0809 1897{
cb338d06 1898 struct mount *tree;
97216be0 1899 namespace_lock();
cd4a4017
EB
1900 if (!check_mnt(real_mount(path->mnt)))
1901 tree = ERR_PTR(-EINVAL);
1902 else
1903 tree = copy_tree(real_mount(path->mnt), path->dentry,
1904 CL_COPY_ALL | CL_PRIVATE);
328e6d90 1905 namespace_unlock();
be34d1a3 1906 if (IS_ERR(tree))
52e220d3 1907 return ERR_CAST(tree);
be34d1a3 1908 return &tree->mnt;
8aec0809
AV
1909}
1910
a07b2000
AV
1911static void free_mnt_ns(struct mnt_namespace *);
1912static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
1913
1914void dissolve_on_fput(struct vfsmount *mnt)
1915{
1916 struct mnt_namespace *ns;
1917 namespace_lock();
1918 lock_mount_hash();
1919 ns = real_mount(mnt)->mnt_ns;
44dfd84a
DH
1920 if (ns) {
1921 if (is_anon_ns(ns))
1922 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
1923 else
1924 ns = NULL;
1925 }
a07b2000
AV
1926 unlock_mount_hash();
1927 namespace_unlock();
44dfd84a
DH
1928 if (ns)
1929 free_mnt_ns(ns);
a07b2000
AV
1930}
1931
8aec0809
AV
1932void drop_collected_mounts(struct vfsmount *mnt)
1933{
97216be0 1934 namespace_lock();
719ea2fb 1935 lock_mount_hash();
9c8e0a1b 1936 umount_tree(real_mount(mnt), 0);
719ea2fb 1937 unlock_mount_hash();
3ab6abee 1938 namespace_unlock();
8aec0809
AV
1939}
1940
c771d683
MS
1941/**
1942 * clone_private_mount - create a private clone of a path
1f287bc4 1943 * @path: path to clone
c771d683 1944 *
1f287bc4
RD
1945 * This creates a new vfsmount, which will be the clone of @path. The new mount
1946 * will not be attached anywhere in the namespace and will be private (i.e.
1947 * changes to the originating mount won't be propagated into this).
c771d683
MS
1948 *
1949 * Release with mntput().
1950 */
ca71cf71 1951struct vfsmount *clone_private_mount(const struct path *path)
c771d683
MS
1952{
1953 struct mount *old_mnt = real_mount(path->mnt);
1954 struct mount *new_mnt;
1955
1956 if (IS_MNT_UNBINDABLE(old_mnt))
1957 return ERR_PTR(-EINVAL);
1958
c771d683 1959 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
c771d683
MS
1960 if (IS_ERR(new_mnt))
1961 return ERR_CAST(new_mnt);
1962
df820f8d
MS
1963 /* Longterm mount to be removed by kern_unmount*() */
1964 new_mnt->mnt_ns = MNT_NS_INTERNAL;
1965
c771d683
MS
1966 return &new_mnt->mnt;
1967}
1968EXPORT_SYMBOL_GPL(clone_private_mount);
1969
1f707137
AV
1970int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1971 struct vfsmount *root)
1972{
1a4eeaf2 1973 struct mount *mnt;
1f707137
AV
1974 int res = f(root, arg);
1975 if (res)
1976 return res;
1a4eeaf2
AV
1977 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1978 res = f(&mnt->mnt, arg);
1f707137
AV
1979 if (res)
1980 return res;
1981 }
1982 return 0;
1983}
1984
3bd045cc
AV
1985static void lock_mnt_tree(struct mount *mnt)
1986{
1987 struct mount *p;
1988
1989 for (p = mnt; p; p = next_mnt(p, mnt)) {
1990 int flags = p->mnt.mnt_flags;
1991 /* Don't allow unprivileged users to change mount flags */
1992 flags |= MNT_LOCK_ATIME;
1993
1994 if (flags & MNT_READONLY)
1995 flags |= MNT_LOCK_READONLY;
1996
1997 if (flags & MNT_NODEV)
1998 flags |= MNT_LOCK_NODEV;
1999
2000 if (flags & MNT_NOSUID)
2001 flags |= MNT_LOCK_NOSUID;
2002
2003 if (flags & MNT_NOEXEC)
2004 flags |= MNT_LOCK_NOEXEC;
2005 /* Don't allow unprivileged users to reveal what is under a mount */
2006 if (list_empty(&p->mnt_expire))
2007 flags |= MNT_LOCKED;
2008 p->mnt.mnt_flags = flags;
2009 }
2010}
2011
4b8b21f4 2012static void cleanup_group_ids(struct mount *mnt, struct mount *end)
719f5d7f 2013{
315fc83e 2014 struct mount *p;
719f5d7f 2015
909b0a88 2016 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
fc7be130 2017 if (p->mnt_group_id && !IS_MNT_SHARED(p))
4b8b21f4 2018 mnt_release_group_id(p);
719f5d7f
MS
2019 }
2020}
2021
4b8b21f4 2022static int invent_group_ids(struct mount *mnt, bool recurse)
719f5d7f 2023{
315fc83e 2024 struct mount *p;
719f5d7f 2025
909b0a88 2026 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
fc7be130 2027 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
4b8b21f4 2028 int err = mnt_alloc_group_id(p);
719f5d7f 2029 if (err) {
4b8b21f4 2030 cleanup_group_ids(mnt, p);
719f5d7f
MS
2031 return err;
2032 }
2033 }
2034 }
2035
2036 return 0;
2037}
2038
d2921684
EB
2039int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2040{
2041 unsigned int max = READ_ONCE(sysctl_mount_max);
2042 unsigned int mounts = 0, old, pending, sum;
2043 struct mount *p;
2044
2045 for (p = mnt; p; p = next_mnt(p, mnt))
2046 mounts++;
2047
2048 old = ns->mounts;
2049 pending = ns->pending_mounts;
2050 sum = old + pending;
2051 if ((old > sum) ||
2052 (pending > sum) ||
2053 (max < sum) ||
2054 (mounts > (max - sum)))
2055 return -ENOSPC;
2056
2057 ns->pending_mounts = pending + mounts;
2058 return 0;
2059}
2060
b90fa9ae
RP
2061/*
2062 * @source_mnt : mount tree to be attached
21444403
RP
2063 * @nd : place the mount tree @source_mnt is attached
2064 * @parent_nd : if non-null, detach the source_mnt from its parent and
2065 * store the parent mount and mountpoint dentry.
2066 * (done when source_mnt is moved)
b90fa9ae
RP
2067 *
2068 * NOTE: in the table below explains the semantics when a source mount
2069 * of a given type is attached to a destination mount of a given type.
9676f0c6
RP
2070 * ---------------------------------------------------------------------------
2071 * | BIND MOUNT OPERATION |
2072 * |**************************************************************************
2073 * | source-->| shared | private | slave | unbindable |
2074 * | dest | | | | |
2075 * | | | | | | |
2076 * | v | | | | |
2077 * |**************************************************************************
2078 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2079 * | | | | | |
2080 * |non-shared| shared (+) | private | slave (*) | invalid |
2081 * ***************************************************************************
b90fa9ae
RP
2082 * A bind operation clones the source mount and mounts the clone on the
2083 * destination mount.
2084 *
2085 * (++) the cloned mount is propagated to all the mounts in the propagation
2086 * tree of the destination mount and the cloned mount is added to
2087 * the peer group of the source mount.
2088 * (+) the cloned mount is created under the destination mount and is marked
2089 * as shared. The cloned mount is added to the peer group of the source
2090 * mount.
5afe0022
RP
2091 * (+++) the mount is propagated to all the mounts in the propagation tree
2092 * of the destination mount and the cloned mount is made slave
2093 * of the same master as that of the source mount. The cloned mount
2094 * is marked as 'shared and slave'.
2095 * (*) the cloned mount is made a slave of the same master as that of the
2096 * source mount.
2097 *
9676f0c6
RP
2098 * ---------------------------------------------------------------------------
2099 * | MOVE MOUNT OPERATION |
2100 * |**************************************************************************
2101 * | source-->| shared | private | slave | unbindable |
2102 * | dest | | | | |
2103 * | | | | | | |
2104 * | v | | | | |
2105 * |**************************************************************************
2106 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2107 * | | | | | |
2108 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2109 * ***************************************************************************
5afe0022
RP
2110 *
2111 * (+) the mount is moved to the destination. And is then propagated to
2112 * all the mounts in the propagation tree of the destination mount.
21444403 2113 * (+*) the mount is moved to the destination.
5afe0022
RP
2114 * (+++) the mount is moved to the destination and is then propagated to
2115 * all the mounts belonging to the destination mount's propagation tree.
2116 * the mount is marked as 'shared and slave'.
2117 * (*) the mount continues to be a slave at the new location.
b90fa9ae
RP
2118 *
2119 * if the source mount is a tree, the operations explained above is
2120 * applied to each mount in the tree.
2121 * Must be called without spinlocks held, since this function can sleep
2122 * in allocations.
2123 */
0fb54e50 2124static int attach_recursive_mnt(struct mount *source_mnt,
84d17192
AV
2125 struct mount *dest_mnt,
2126 struct mountpoint *dest_mp,
2763d119 2127 bool moving)
b90fa9ae 2128{
3bd045cc 2129 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
38129a13 2130 HLIST_HEAD(tree_list);
d2921684 2131 struct mnt_namespace *ns = dest_mnt->mnt_ns;
1064f874 2132 struct mountpoint *smp;
315fc83e 2133 struct mount *child, *p;
38129a13 2134 struct hlist_node *n;
719f5d7f 2135 int err;
b90fa9ae 2136
1064f874
EB
2137 /* Preallocate a mountpoint in case the new mounts need
2138 * to be tucked under other mounts.
2139 */
2140 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2141 if (IS_ERR(smp))
2142 return PTR_ERR(smp);
2143
d2921684 2144 /* Is there space to add these mounts to the mount namespace? */
2763d119 2145 if (!moving) {
d2921684
EB
2146 err = count_mounts(ns, source_mnt);
2147 if (err)
2148 goto out;
2149 }
2150
fc7be130 2151 if (IS_MNT_SHARED(dest_mnt)) {
0fb54e50 2152 err = invent_group_ids(source_mnt, true);
719f5d7f
MS
2153 if (err)
2154 goto out;
0b1b901b 2155 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
f2ebb3a9 2156 lock_mount_hash();
0b1b901b
AV
2157 if (err)
2158 goto out_cleanup_ids;
909b0a88 2159 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
0f0afb1d 2160 set_mnt_shared(p);
0b1b901b
AV
2161 } else {
2162 lock_mount_hash();
b90fa9ae 2163 }
2763d119
AV
2164 if (moving) {
2165 unhash_mnt(source_mnt);
84d17192 2166 attach_mnt(source_mnt, dest_mnt, dest_mp);
143c8c91 2167 touch_mnt_namespace(source_mnt->mnt_ns);
21444403 2168 } else {
44dfd84a
DH
2169 if (source_mnt->mnt_ns) {
2170 /* move from anon - the caller will destroy */
2171 list_del_init(&source_mnt->mnt_ns->list);
2172 }
84d17192 2173 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1064f874 2174 commit_tree(source_mnt);
21444403 2175 }
b90fa9ae 2176
38129a13 2177 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
1d6a32ac 2178 struct mount *q;
38129a13 2179 hlist_del_init(&child->mnt_hash);
1064f874
EB
2180 q = __lookup_mnt(&child->mnt_parent->mnt,
2181 child->mnt_mountpoint);
2182 if (q)
2183 mnt_change_mountpoint(child, smp, q);
3bd045cc
AV
2184 /* Notice when we are propagating across user namespaces */
2185 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2186 lock_mnt_tree(child);
d728cf79 2187 child->mnt.mnt_flags &= ~MNT_LOCKED;
1064f874 2188 commit_tree(child);
b90fa9ae 2189 }
1064f874 2190 put_mountpoint(smp);
719ea2fb 2191 unlock_mount_hash();
99b7db7b 2192
b90fa9ae 2193 return 0;
719f5d7f
MS
2194
2195 out_cleanup_ids:
f2ebb3a9
AV
2196 while (!hlist_empty(&tree_list)) {
2197 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
d2921684 2198 child->mnt_parent->mnt_ns->pending_mounts = 0;
e819f152 2199 umount_tree(child, UMOUNT_SYNC);
f2ebb3a9
AV
2200 }
2201 unlock_mount_hash();
0b1b901b 2202 cleanup_group_ids(source_mnt, NULL);
719f5d7f 2203 out:
d2921684 2204 ns->pending_mounts = 0;
1064f874
EB
2205
2206 read_seqlock_excl(&mount_lock);
2207 put_mountpoint(smp);
2208 read_sequnlock_excl(&mount_lock);
2209
719f5d7f 2210 return err;
b90fa9ae
RP
2211}
2212
84d17192 2213static struct mountpoint *lock_mount(struct path *path)
b12cea91
AV
2214{
2215 struct vfsmount *mnt;
84d17192 2216 struct dentry *dentry = path->dentry;
b12cea91 2217retry:
5955102c 2218 inode_lock(dentry->d_inode);
84d17192 2219 if (unlikely(cant_mount(dentry))) {
5955102c 2220 inode_unlock(dentry->d_inode);
84d17192 2221 return ERR_PTR(-ENOENT);
b12cea91 2222 }
97216be0 2223 namespace_lock();
b12cea91 2224 mnt = lookup_mnt(path);
84d17192 2225 if (likely(!mnt)) {
3895dbf8 2226 struct mountpoint *mp = get_mountpoint(dentry);
84d17192 2227 if (IS_ERR(mp)) {
97216be0 2228 namespace_unlock();
5955102c 2229 inode_unlock(dentry->d_inode);
84d17192
AV
2230 return mp;
2231 }
2232 return mp;
2233 }
97216be0 2234 namespace_unlock();
5955102c 2235 inode_unlock(path->dentry->d_inode);
b12cea91
AV
2236 path_put(path);
2237 path->mnt = mnt;
84d17192 2238 dentry = path->dentry = dget(mnt->mnt_root);
b12cea91
AV
2239 goto retry;
2240}
2241
84d17192 2242static void unlock_mount(struct mountpoint *where)
b12cea91 2243{
84d17192 2244 struct dentry *dentry = where->m_dentry;
3895dbf8
EB
2245
2246 read_seqlock_excl(&mount_lock);
84d17192 2247 put_mountpoint(where);
3895dbf8
EB
2248 read_sequnlock_excl(&mount_lock);
2249
328e6d90 2250 namespace_unlock();
5955102c 2251 inode_unlock(dentry->d_inode);
b12cea91
AV
2252}
2253
84d17192 2254static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1da177e4 2255{
e462ec50 2256 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
1da177e4
LT
2257 return -EINVAL;
2258
e36cb0b8
DH
2259 if (d_is_dir(mp->m_dentry) !=
2260 d_is_dir(mnt->mnt.mnt_root))
1da177e4
LT
2261 return -ENOTDIR;
2262
2763d119 2263 return attach_recursive_mnt(mnt, p, mp, false);
1da177e4
LT
2264}
2265
7a2e8a8f
VA
2266/*
2267 * Sanity check the flags to change_mnt_propagation.
2268 */
2269
e462ec50 2270static int flags_to_propagation_type(int ms_flags)
7a2e8a8f 2271{
e462ec50 2272 int type = ms_flags & ~(MS_REC | MS_SILENT);
7a2e8a8f
VA
2273
2274 /* Fail if any non-propagation flags are set */
2275 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2276 return 0;
2277 /* Only one propagation flag should be set */
2278 if (!is_power_of_2(type))
2279 return 0;
2280 return type;
2281}
2282
07b20889
RP
2283/*
2284 * recursively change the type of the mountpoint.
2285 */
e462ec50 2286static int do_change_type(struct path *path, int ms_flags)
07b20889 2287{
315fc83e 2288 struct mount *m;
4b8b21f4 2289 struct mount *mnt = real_mount(path->mnt);
e462ec50 2290 int recurse = ms_flags & MS_REC;
7a2e8a8f 2291 int type;
719f5d7f 2292 int err = 0;
07b20889 2293
2d92ab3c 2294 if (path->dentry != path->mnt->mnt_root)
07b20889
RP
2295 return -EINVAL;
2296
e462ec50 2297 type = flags_to_propagation_type(ms_flags);
7a2e8a8f
VA
2298 if (!type)
2299 return -EINVAL;
2300
97216be0 2301 namespace_lock();
719f5d7f
MS
2302 if (type == MS_SHARED) {
2303 err = invent_group_ids(mnt, recurse);
2304 if (err)
2305 goto out_unlock;
2306 }
2307
719ea2fb 2308 lock_mount_hash();
909b0a88 2309 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
0f0afb1d 2310 change_mnt_propagation(m, type);
719ea2fb 2311 unlock_mount_hash();
719f5d7f
MS
2312
2313 out_unlock:
97216be0 2314 namespace_unlock();
719f5d7f 2315 return err;
07b20889
RP
2316}
2317
5ff9d8a6
EB
2318static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2319{
2320 struct mount *child;
2321 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2322 if (!is_subdir(child->mnt_mountpoint, dentry))
2323 continue;
2324
2325 if (child->mnt.mnt_flags & MNT_LOCKED)
2326 return true;
2327 }
2328 return false;
2329}
2330
a07b2000
AV
2331static struct mount *__do_loopback(struct path *old_path, int recurse)
2332{
2333 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2334
2335 if (IS_MNT_UNBINDABLE(old))
2336 return mnt;
2337
2338 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2339 return mnt;
2340
2341 if (!recurse && has_locked_children(old, old_path->dentry))
2342 return mnt;
2343
2344 if (recurse)
2345 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2346 else
2347 mnt = clone_mnt(old, old_path->dentry, 0);
2348
2349 if (!IS_ERR(mnt))
2350 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2351
2352 return mnt;
2353}
2354
1da177e4
LT
2355/*
2356 * do loopback mount.
2357 */
808d4e3c 2358static int do_loopback(struct path *path, const char *old_name,
2dafe1c4 2359 int recurse)
1da177e4 2360{
2d92ab3c 2361 struct path old_path;
a07b2000 2362 struct mount *mnt = NULL, *parent;
84d17192 2363 struct mountpoint *mp;
57eccb83 2364 int err;
1da177e4
LT
2365 if (!old_name || !*old_name)
2366 return -EINVAL;
815d405c 2367 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1da177e4
LT
2368 if (err)
2369 return err;
2370
8823c079 2371 err = -EINVAL;
4ce5d2b1 2372 if (mnt_ns_loop(old_path.dentry))
dd111b31 2373 goto out;
8823c079 2374
84d17192 2375 mp = lock_mount(path);
a07b2000
AV
2376 if (IS_ERR(mp)) {
2377 err = PTR_ERR(mp);
b12cea91 2378 goto out;
a07b2000 2379 }
b12cea91 2380
84d17192 2381 parent = real_mount(path->mnt);
e149ed2b
AV
2382 if (!check_mnt(parent))
2383 goto out2;
2384
a07b2000 2385 mnt = __do_loopback(&old_path, recurse);
be34d1a3
DH
2386 if (IS_ERR(mnt)) {
2387 err = PTR_ERR(mnt);
e9c5d8a5 2388 goto out2;
be34d1a3 2389 }
ccd48bc7 2390
84d17192 2391 err = graft_tree(mnt, parent, mp);
ccd48bc7 2392 if (err) {
719ea2fb 2393 lock_mount_hash();
e819f152 2394 umount_tree(mnt, UMOUNT_SYNC);
719ea2fb 2395 unlock_mount_hash();
5b83d2c5 2396 }
b12cea91 2397out2:
84d17192 2398 unlock_mount(mp);
ccd48bc7 2399out:
2d92ab3c 2400 path_put(&old_path);
1da177e4
LT
2401 return err;
2402}
2403
a07b2000
AV
2404static struct file *open_detached_copy(struct path *path, bool recursive)
2405{
2406 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2407 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2408 struct mount *mnt, *p;
2409 struct file *file;
2410
2411 if (IS_ERR(ns))
2412 return ERR_CAST(ns);
2413
2414 namespace_lock();
2415 mnt = __do_loopback(path, recursive);
2416 if (IS_ERR(mnt)) {
2417 namespace_unlock();
2418 free_mnt_ns(ns);
2419 return ERR_CAST(mnt);
2420 }
2421
2422 lock_mount_hash();
2423 for (p = mnt; p; p = next_mnt(p, mnt)) {
2424 p->mnt_ns = ns;
2425 ns->mounts++;
2426 }
2427 ns->root = mnt;
2428 list_add_tail(&ns->list, &mnt->mnt_list);
2429 mntget(&mnt->mnt);
2430 unlock_mount_hash();
2431 namespace_unlock();
2432
2433 mntput(path->mnt);
2434 path->mnt = &mnt->mnt;
2435 file = dentry_open(path, O_PATH, current_cred());
2436 if (IS_ERR(file))
2437 dissolve_on_fput(path->mnt);
2438 else
2439 file->f_mode |= FMODE_NEED_UNMOUNT;
2440 return file;
2441}
2442
2658ce09 2443SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
a07b2000
AV
2444{
2445 struct file *file;
2446 struct path path;
2447 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2448 bool detached = flags & OPEN_TREE_CLONE;
2449 int error;
2450 int fd;
2451
2452 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2453
2454 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2455 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2456 OPEN_TREE_CLOEXEC))
2457 return -EINVAL;
2458
2459 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2460 return -EINVAL;
2461
2462 if (flags & AT_NO_AUTOMOUNT)
2463 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2464 if (flags & AT_SYMLINK_NOFOLLOW)
2465 lookup_flags &= ~LOOKUP_FOLLOW;
2466 if (flags & AT_EMPTY_PATH)
2467 lookup_flags |= LOOKUP_EMPTY;
2468
2469 if (detached && !may_mount())
2470 return -EPERM;
2471
2472 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2473 if (fd < 0)
2474 return fd;
2475
2476 error = user_path_at(dfd, filename, lookup_flags, &path);
2477 if (unlikely(error)) {
2478 file = ERR_PTR(error);
2479 } else {
2480 if (detached)
2481 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2482 else
2483 file = dentry_open(&path, O_PATH, current_cred());
2484 path_put(&path);
2485 }
2486 if (IS_ERR(file)) {
2487 put_unused_fd(fd);
2488 return PTR_ERR(file);
2489 }
2490 fd_install(fd, file);
2491 return fd;
2492}
2493
43f5e655
DH
2494/*
2495 * Don't allow locked mount flags to be cleared.
2496 *
2497 * No locks need to be held here while testing the various MNT_LOCK
2498 * flags because those flags can never be cleared once they are set.
2499 */
2500static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2e4b7fcd 2501{
43f5e655
DH
2502 unsigned int fl = mnt->mnt.mnt_flags;
2503
2504 if ((fl & MNT_LOCK_READONLY) &&
2505 !(mnt_flags & MNT_READONLY))
2506 return false;
2507
2508 if ((fl & MNT_LOCK_NODEV) &&
2509 !(mnt_flags & MNT_NODEV))
2510 return false;
2511
2512 if ((fl & MNT_LOCK_NOSUID) &&
2513 !(mnt_flags & MNT_NOSUID))
2514 return false;
2515
2516 if ((fl & MNT_LOCK_NOEXEC) &&
2517 !(mnt_flags & MNT_NOEXEC))
2518 return false;
2519
2520 if ((fl & MNT_LOCK_ATIME) &&
2521 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2522 return false;
2e4b7fcd 2523
43f5e655
DH
2524 return true;
2525}
2526
2527static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2e4b7fcd 2528{
43f5e655 2529 bool readonly_request = (mnt_flags & MNT_READONLY);
2e4b7fcd 2530
43f5e655 2531 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2e4b7fcd
DH
2532 return 0;
2533
2534 if (readonly_request)
43f5e655
DH
2535 return mnt_make_readonly(mnt);
2536
68847c94
CB
2537 mnt->mnt.mnt_flags &= ~MNT_READONLY;
2538 return 0;
43f5e655
DH
2539}
2540
43f5e655
DH
2541static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2542{
43f5e655
DH
2543 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2544 mnt->mnt.mnt_flags = mnt_flags;
2545 touch_mnt_namespace(mnt->mnt_ns);
43f5e655
DH
2546}
2547
f8b92ba6
DD
2548static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2549{
2550 struct super_block *sb = mnt->mnt_sb;
2551
2552 if (!__mnt_is_readonly(mnt) &&
2553 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2554 char *buf = (char *)__get_free_page(GFP_KERNEL);
2555 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2556 struct tm tm;
2557
2558 time64_to_tm(sb->s_time_max, 0, &tm);
2559
0ecee669
EB
2560 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2561 sb->s_type->name,
2562 is_mounted(mnt) ? "remounted" : "mounted",
2563 mntpath,
f8b92ba6
DD
2564 tm.tm_year+1900, (unsigned long long)sb->s_time_max);
2565
2566 free_page((unsigned long)buf);
2567 }
2568}
2569
43f5e655
DH
2570/*
2571 * Handle reconfiguration of the mountpoint only without alteration of the
2572 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2573 * to mount(2).
2574 */
2575static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2576{
2577 struct super_block *sb = path->mnt->mnt_sb;
2578 struct mount *mnt = real_mount(path->mnt);
2579 int ret;
2580
2581 if (!check_mnt(mnt))
2582 return -EINVAL;
2583
2584 if (path->dentry != mnt->mnt.mnt_root)
2585 return -EINVAL;
2586
2587 if (!can_change_locked_flags(mnt, mnt_flags))
2588 return -EPERM;
2589
e58ace1a
CB
2590 /*
2591 * We're only checking whether the superblock is read-only not
2592 * changing it, so only take down_read(&sb->s_umount).
2593 */
2594 down_read(&sb->s_umount);
68847c94 2595 lock_mount_hash();
43f5e655
DH
2596 ret = change_mount_ro_state(mnt, mnt_flags);
2597 if (ret == 0)
2598 set_mount_attributes(mnt, mnt_flags);
68847c94 2599 unlock_mount_hash();
e58ace1a 2600 up_read(&sb->s_umount);
f8b92ba6
DD
2601
2602 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2603
43f5e655 2604 return ret;
2e4b7fcd
DH
2605}
2606
1da177e4
LT
2607/*
2608 * change filesystem flags. dir should be a physical root of filesystem.
2609 * If you've mounted a non-root directory somewhere and want to do remount
2610 * on it - tough luck.
2611 */
e462ec50
DH
2612static int do_remount(struct path *path, int ms_flags, int sb_flags,
2613 int mnt_flags, void *data)
1da177e4
LT
2614{
2615 int err;
2d92ab3c 2616 struct super_block *sb = path->mnt->mnt_sb;
143c8c91 2617 struct mount *mnt = real_mount(path->mnt);
8d0347f6 2618 struct fs_context *fc;
1da177e4 2619
143c8c91 2620 if (!check_mnt(mnt))
1da177e4
LT
2621 return -EINVAL;
2622
2d92ab3c 2623 if (path->dentry != path->mnt->mnt_root)
1da177e4
LT
2624 return -EINVAL;
2625
43f5e655 2626 if (!can_change_locked_flags(mnt, mnt_flags))
9566d674 2627 return -EPERM;
9566d674 2628
8d0347f6
DH
2629 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2630 if (IS_ERR(fc))
2631 return PTR_ERR(fc);
ff36fe2c 2632
b330966f 2633 fc->oldapi = true;
8d0347f6
DH
2634 err = parse_monolithic_mount_data(fc, data);
2635 if (!err) {
2636 down_write(&sb->s_umount);
2637 err = -EPERM;
2638 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2639 err = reconfigure_super(fc);
68847c94
CB
2640 if (!err) {
2641 lock_mount_hash();
8d0347f6 2642 set_mount_attributes(mnt, mnt_flags);
68847c94
CB
2643 unlock_mount_hash();
2644 }
8d0347f6
DH
2645 }
2646 up_write(&sb->s_umount);
0e55a7cc 2647 }
f8b92ba6
DD
2648
2649 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2650
8d0347f6 2651 put_fs_context(fc);
1da177e4
LT
2652 return err;
2653}
2654
cbbe362c 2655static inline int tree_contains_unbindable(struct mount *mnt)
9676f0c6 2656{
315fc83e 2657 struct mount *p;
909b0a88 2658 for (p = mnt; p; p = next_mnt(p, mnt)) {
fc7be130 2659 if (IS_MNT_UNBINDABLE(p))
9676f0c6
RP
2660 return 1;
2661 }
2662 return 0;
2663}
2664
44dfd84a
DH
2665/*
2666 * Check that there aren't references to earlier/same mount namespaces in the
2667 * specified subtree. Such references can act as pins for mount namespaces
2668 * that aren't checked by the mount-cycle checking code, thereby allowing
2669 * cycles to be made.
2670 */
2671static bool check_for_nsfs_mounts(struct mount *subtree)
2672{
2673 struct mount *p;
2674 bool ret = false;
2675
2676 lock_mount_hash();
2677 for (p = subtree; p; p = next_mnt(p, subtree))
2678 if (mnt_ns_loop(p->mnt.mnt_root))
2679 goto out;
2680
2681 ret = true;
2682out:
2683 unlock_mount_hash();
2684 return ret;
2685}
2686
2db154b3 2687static int do_move_mount(struct path *old_path, struct path *new_path)
1da177e4 2688{
44dfd84a 2689 struct mnt_namespace *ns;
676da58d 2690 struct mount *p;
0fb54e50 2691 struct mount *old;
2763d119
AV
2692 struct mount *parent;
2693 struct mountpoint *mp, *old_mp;
57eccb83 2694 int err;
44dfd84a 2695 bool attached;
1da177e4 2696
2db154b3 2697 mp = lock_mount(new_path);
84d17192 2698 if (IS_ERR(mp))
2db154b3 2699 return PTR_ERR(mp);
cc53ce53 2700
2db154b3
DH
2701 old = real_mount(old_path->mnt);
2702 p = real_mount(new_path->mnt);
2763d119 2703 parent = old->mnt_parent;
44dfd84a 2704 attached = mnt_has_parent(old);
2763d119 2705 old_mp = old->mnt_mp;
44dfd84a 2706 ns = old->mnt_ns;
143c8c91 2707
1da177e4 2708 err = -EINVAL;
44dfd84a
DH
2709 /* The mountpoint must be in our namespace. */
2710 if (!check_mnt(p))
2db154b3 2711 goto out;
1da177e4 2712
570d7a98
EB
2713 /* The thing moved must be mounted... */
2714 if (!is_mounted(&old->mnt))
44dfd84a
DH
2715 goto out;
2716
570d7a98
EB
2717 /* ... and either ours or the root of anon namespace */
2718 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
2db154b3 2719 goto out;
5ff9d8a6 2720
2db154b3
DH
2721 if (old->mnt.mnt_flags & MNT_LOCKED)
2722 goto out;
1da177e4 2723
2db154b3
DH
2724 if (old_path->dentry != old_path->mnt->mnt_root)
2725 goto out;
1da177e4 2726
2db154b3
DH
2727 if (d_is_dir(new_path->dentry) !=
2728 d_is_dir(old_path->dentry))
2729 goto out;
21444403
RP
2730 /*
2731 * Don't move a mount residing in a shared parent.
2732 */
2763d119 2733 if (attached && IS_MNT_SHARED(parent))
2db154b3 2734 goto out;
9676f0c6
RP
2735 /*
2736 * Don't move a mount tree containing unbindable mounts to a destination
2737 * mount which is shared.
2738 */
fc7be130 2739 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2db154b3 2740 goto out;
1da177e4 2741 err = -ELOOP;
44dfd84a
DH
2742 if (!check_for_nsfs_mounts(old))
2743 goto out;
fc7be130 2744 for (; mnt_has_parent(p); p = p->mnt_parent)
676da58d 2745 if (p == old)
2db154b3 2746 goto out;
1da177e4 2747
2db154b3 2748 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
2763d119 2749 attached);
4ac91378 2750 if (err)
2db154b3 2751 goto out;
1da177e4
LT
2752
2753 /* if the mount is moved, it should no longer be expire
2754 * automatically */
6776db3d 2755 list_del_init(&old->mnt_expire);
2763d119
AV
2756 if (attached)
2757 put_mountpoint(old_mp);
1da177e4 2758out:
2db154b3 2759 unlock_mount(mp);
44dfd84a 2760 if (!err) {
2763d119
AV
2761 if (attached)
2762 mntput_no_expire(parent);
2763 else
44dfd84a
DH
2764 free_mnt_ns(ns);
2765 }
2db154b3
DH
2766 return err;
2767}
2768
2769static int do_move_mount_old(struct path *path, const char *old_name)
2770{
2771 struct path old_path;
2772 int err;
2773
2774 if (!old_name || !*old_name)
2775 return -EINVAL;
2776
2777 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2778 if (err)
2779 return err;
2780
2781 err = do_move_mount(&old_path, path);
2d92ab3c 2782 path_put(&old_path);
1da177e4
LT
2783 return err;
2784}
2785
9d412a43
AV
2786/*
2787 * add a mount into a namespace's mount tree
2788 */
8f11538e
AV
2789static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
2790 struct path *path, int mnt_flags)
9d412a43 2791{
8f11538e 2792 struct mount *parent = real_mount(path->mnt);
9d412a43 2793
f2ebb3a9 2794 mnt_flags &= ~MNT_INTERNAL_FLAGS;
9d412a43 2795
84d17192 2796 if (unlikely(!check_mnt(parent))) {
156cacb1
AV
2797 /* that's acceptable only for automounts done in private ns */
2798 if (!(mnt_flags & MNT_SHRINKABLE))
8f11538e 2799 return -EINVAL;
156cacb1 2800 /* ... and for those we'd better have mountpoint still alive */
84d17192 2801 if (!parent->mnt_ns)
8f11538e 2802 return -EINVAL;
156cacb1 2803 }
9d412a43
AV
2804
2805 /* Refuse the same filesystem on the same mount point */
95bc5f25 2806 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
9d412a43 2807 path->mnt->mnt_root == path->dentry)
8f11538e 2808 return -EBUSY;
9d412a43 2809
e36cb0b8 2810 if (d_is_symlink(newmnt->mnt.mnt_root))
8f11538e 2811 return -EINVAL;
9d412a43 2812
95bc5f25 2813 newmnt->mnt.mnt_flags = mnt_flags;
8f11538e 2814 return graft_tree(newmnt, parent, mp);
9d412a43 2815}
b1e75df4 2816
132e4608
DH
2817static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
2818
2819/*
2820 * Create a new mount using a superblock configuration and request it
2821 * be added to the namespace tree.
2822 */
2823static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
2824 unsigned int mnt_flags)
2825{
2826 struct vfsmount *mnt;
8f11538e 2827 struct mountpoint *mp;
132e4608
DH
2828 struct super_block *sb = fc->root->d_sb;
2829 int error;
2830
c9ce29ed
AV
2831 error = security_sb_kern_mount(sb);
2832 if (!error && mount_too_revealing(sb, &mnt_flags))
2833 error = -EPERM;
2834
2835 if (unlikely(error)) {
2836 fc_drop_locked(fc);
2837 return error;
132e4608
DH
2838 }
2839
2840 up_write(&sb->s_umount);
2841
2842 mnt = vfs_create_mount(fc);
2843 if (IS_ERR(mnt))
2844 return PTR_ERR(mnt);
2845
f8b92ba6
DD
2846 mnt_warn_timestamp_expiry(mountpoint, mnt);
2847
8f11538e
AV
2848 mp = lock_mount(mountpoint);
2849 if (IS_ERR(mp)) {
2850 mntput(mnt);
2851 return PTR_ERR(mp);
2852 }
2853 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
2854 unlock_mount(mp);
0ecee669
EB
2855 if (error < 0)
2856 mntput(mnt);
132e4608
DH
2857 return error;
2858}
1b852bce 2859
1da177e4
LT
2860/*
2861 * create a new mount for userspace and request it to be added into the
2862 * namespace's tree
2863 */
e462ec50 2864static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
808d4e3c 2865 int mnt_flags, const char *name, void *data)
1da177e4 2866{
0c55cfc4 2867 struct file_system_type *type;
a0c9a8b8
AV
2868 struct fs_context *fc;
2869 const char *subtype = NULL;
2870 int err = 0;
1da177e4 2871
0c55cfc4 2872 if (!fstype)
1da177e4
LT
2873 return -EINVAL;
2874
0c55cfc4
EB
2875 type = get_fs_type(fstype);
2876 if (!type)
2877 return -ENODEV;
2878
a0c9a8b8
AV
2879 if (type->fs_flags & FS_HAS_SUBTYPE) {
2880 subtype = strchr(fstype, '.');
2881 if (subtype) {
2882 subtype++;
2883 if (!*subtype) {
2884 put_filesystem(type);
2885 return -EINVAL;
2886 }
a0c9a8b8
AV
2887 }
2888 }
0c55cfc4 2889
a0c9a8b8 2890 fc = fs_context_for_mount(type, sb_flags);
0c55cfc4 2891 put_filesystem(type);
a0c9a8b8
AV
2892 if (IS_ERR(fc))
2893 return PTR_ERR(fc);
2894
3e1aeb00
DH
2895 if (subtype)
2896 err = vfs_parse_fs_string(fc, "subtype",
2897 subtype, strlen(subtype));
2898 if (!err && name)
2899 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
a0c9a8b8
AV
2900 if (!err)
2901 err = parse_monolithic_mount_data(fc, data);
c3aabf07
AV
2902 if (!err && !mount_capable(fc))
2903 err = -EPERM;
a0c9a8b8
AV
2904 if (!err)
2905 err = vfs_get_tree(fc);
132e4608
DH
2906 if (!err)
2907 err = do_new_mount_fc(fc, path, mnt_flags);
8654df4e 2908
a0c9a8b8 2909 put_fs_context(fc);
15f9a3f3 2910 return err;
1da177e4
LT
2911}
2912
19a167af
AV
2913int finish_automount(struct vfsmount *m, struct path *path)
2914{
26df6034 2915 struct dentry *dentry = path->dentry;
8f11538e 2916 struct mountpoint *mp;
25e195aa 2917 struct mount *mnt;
19a167af 2918 int err;
25e195aa
AV
2919
2920 if (!m)
2921 return 0;
2922 if (IS_ERR(m))
2923 return PTR_ERR(m);
2924
2925 mnt = real_mount(m);
19a167af
AV
2926 /* The new mount record should have at least 2 refs to prevent it being
2927 * expired before we get a chance to add it
2928 */
6776db3d 2929 BUG_ON(mnt_get_count(mnt) < 2);
19a167af
AV
2930
2931 if (m->mnt_sb == path->mnt->mnt_sb &&
26df6034 2932 m->mnt_root == dentry) {
b1e75df4 2933 err = -ELOOP;
26df6034 2934 goto discard;
19a167af
AV
2935 }
2936
26df6034
AV
2937 /*
2938 * we don't want to use lock_mount() - in this case finding something
2939 * that overmounts our mountpoint to be means "quitely drop what we've
2940 * got", not "try to mount it on top".
2941 */
2942 inode_lock(dentry->d_inode);
2943 namespace_lock();
2944 if (unlikely(cant_mount(dentry))) {
2945 err = -ENOENT;
2946 goto discard_locked;
2947 }
2948 rcu_read_lock();
2949 if (unlikely(__lookup_mnt(path->mnt, dentry))) {
2950 rcu_read_unlock();
2951 err = 0;
2952 goto discard_locked;
2953 }
2954 rcu_read_unlock();
2955 mp = get_mountpoint(dentry);
8f11538e
AV
2956 if (IS_ERR(mp)) {
2957 err = PTR_ERR(mp);
26df6034 2958 goto discard_locked;
8f11538e 2959 }
26df6034 2960
8f11538e
AV
2961 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2962 unlock_mount(mp);
26df6034
AV
2963 if (unlikely(err))
2964 goto discard;
2965 mntput(m);
2966 return 0;
2967
2968discard_locked:
2969 namespace_unlock();
2970 inode_unlock(dentry->d_inode);
2971discard:
b1e75df4 2972 /* remove m from any expiration list it may be on */
6776db3d 2973 if (!list_empty(&mnt->mnt_expire)) {
97216be0 2974 namespace_lock();
6776db3d 2975 list_del_init(&mnt->mnt_expire);
97216be0 2976 namespace_unlock();
19a167af 2977 }
b1e75df4
AV
2978 mntput(m);
2979 mntput(m);
19a167af
AV
2980 return err;
2981}
2982
ea5b778a
DH
2983/**
2984 * mnt_set_expiry - Put a mount on an expiration list
2985 * @mnt: The mount to list.
2986 * @expiry_list: The list to add the mount to.
2987 */
2988void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2989{
97216be0 2990 namespace_lock();
ea5b778a 2991
6776db3d 2992 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
ea5b778a 2993
97216be0 2994 namespace_unlock();
ea5b778a
DH
2995}
2996EXPORT_SYMBOL(mnt_set_expiry);
2997
1da177e4
LT
2998/*
2999 * process a list of expirable mountpoints with the intent of discarding any
3000 * mountpoints that aren't in use and haven't been touched since last we came
3001 * here
3002 */
3003void mark_mounts_for_expiry(struct list_head *mounts)
3004{
761d5c38 3005 struct mount *mnt, *next;
1da177e4
LT
3006 LIST_HEAD(graveyard);
3007
3008 if (list_empty(mounts))
3009 return;
3010
97216be0 3011 namespace_lock();
719ea2fb 3012 lock_mount_hash();
1da177e4
LT
3013
3014 /* extract from the expiration list every vfsmount that matches the
3015 * following criteria:
3016 * - only referenced by its parent vfsmount
3017 * - still marked for expiry (marked on the last call here; marks are
3018 * cleared by mntput())
3019 */
6776db3d 3020 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
863d684f 3021 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
1ab59738 3022 propagate_mount_busy(mnt, 1))
1da177e4 3023 continue;
6776db3d 3024 list_move(&mnt->mnt_expire, &graveyard);
1da177e4 3025 }
bcc5c7d2 3026 while (!list_empty(&graveyard)) {
6776db3d 3027 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
143c8c91 3028 touch_mnt_namespace(mnt->mnt_ns);
e819f152 3029 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
bcc5c7d2 3030 }
719ea2fb 3031 unlock_mount_hash();
3ab6abee 3032 namespace_unlock();
5528f911
TM
3033}
3034
3035EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3036
3037/*
3038 * Ripoff of 'select_parent()'
3039 *
3040 * search the list of submounts for a given mountpoint, and move any
3041 * shrinkable submounts to the 'graveyard' list.
3042 */
692afc31 3043static int select_submounts(struct mount *parent, struct list_head *graveyard)
5528f911 3044{
692afc31 3045 struct mount *this_parent = parent;
5528f911
TM
3046 struct list_head *next;
3047 int found = 0;
3048
3049repeat:
6b41d536 3050 next = this_parent->mnt_mounts.next;
5528f911 3051resume:
6b41d536 3052 while (next != &this_parent->mnt_mounts) {
5528f911 3053 struct list_head *tmp = next;
6b41d536 3054 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
5528f911
TM
3055
3056 next = tmp->next;
692afc31 3057 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
1da177e4 3058 continue;
5528f911
TM
3059 /*
3060 * Descend a level if the d_mounts list is non-empty.
3061 */
6b41d536 3062 if (!list_empty(&mnt->mnt_mounts)) {
5528f911
TM
3063 this_parent = mnt;
3064 goto repeat;
3065 }
1da177e4 3066
1ab59738 3067 if (!propagate_mount_busy(mnt, 1)) {
6776db3d 3068 list_move_tail(&mnt->mnt_expire, graveyard);
5528f911
TM
3069 found++;
3070 }
1da177e4 3071 }
5528f911
TM
3072 /*
3073 * All done at this level ... ascend and resume the search
3074 */
3075 if (this_parent != parent) {
6b41d536 3076 next = this_parent->mnt_child.next;
0714a533 3077 this_parent = this_parent->mnt_parent;
5528f911
TM
3078 goto resume;
3079 }
3080 return found;
3081}
3082
3083/*
3084 * process a list of expirable mountpoints with the intent of discarding any
3085 * submounts of a specific parent mountpoint
99b7db7b 3086 *
48a066e7 3087 * mount_lock must be held for write
5528f911 3088 */
b54b9be7 3089static void shrink_submounts(struct mount *mnt)
5528f911
TM
3090{
3091 LIST_HEAD(graveyard);
761d5c38 3092 struct mount *m;
5528f911 3093
5528f911 3094 /* extract submounts of 'mountpoint' from the expiration list */
c35038be 3095 while (select_submounts(mnt, &graveyard)) {
bcc5c7d2 3096 while (!list_empty(&graveyard)) {
761d5c38 3097 m = list_first_entry(&graveyard, struct mount,
6776db3d 3098 mnt_expire);
143c8c91 3099 touch_mnt_namespace(m->mnt_ns);
e819f152 3100 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
bcc5c7d2
AV
3101 }
3102 }
1da177e4
LT
3103}
3104
028abd92 3105static void *copy_mount_options(const void __user * data)
1da177e4 3106{
b40ef869 3107 char *copy;
d563d678 3108 unsigned left, offset;
b58fed8b 3109
1da177e4 3110 if (!data)
b40ef869 3111 return NULL;
1da177e4 3112
b40ef869
AV
3113 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3114 if (!copy)
3115 return ERR_PTR(-ENOMEM);
1da177e4 3116
d563d678 3117 left = copy_from_user(copy, data, PAGE_SIZE);
1da177e4 3118
d563d678
CM
3119 /*
3120 * Not all architectures have an exact copy_from_user(). Resort to
3121 * byte at a time.
3122 */
3123 offset = PAGE_SIZE - left;
3124 while (left) {
3125 char c;
3126 if (get_user(c, (const char __user *)data + offset))
3127 break;
3128 copy[offset] = c;
3129 left--;
3130 offset++;
3131 }
3132
3133 if (left == PAGE_SIZE) {
b40ef869
AV
3134 kfree(copy);
3135 return ERR_PTR(-EFAULT);
1da177e4 3136 }
d563d678 3137
b40ef869 3138 return copy;
1da177e4
LT
3139}
3140
028abd92 3141static char *copy_mount_string(const void __user *data)
eca6f534 3142{
fbdb4401 3143 return data ? strndup_user(data, PATH_MAX) : NULL;
eca6f534
VN
3144}
3145
1da177e4
LT
3146/*
3147 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3148 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3149 *
3150 * data is a (void *) that can point to any structure up to
3151 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3152 * information (or be NULL).
3153 *
3154 * Pre-0.97 versions of mount() didn't have a flags word.
3155 * When the flags word was introduced its top half was required
3156 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3157 * Therefore, if this magic number is present, it carries no information
3158 * and must be discarded.
3159 */
c60166f0 3160int path_mount(const char *dev_name, struct path *path,
808d4e3c 3161 const char *type_page, unsigned long flags, void *data_page)
1da177e4 3162{
e462ec50 3163 unsigned int mnt_flags = 0, sb_flags;
a1e6aaa3 3164 int ret;
1da177e4
LT
3165
3166 /* Discard magic */
3167 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3168 flags &= ~MS_MGC_MSK;
3169
3170 /* Basic sanity checks */
1da177e4
LT
3171 if (data_page)
3172 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3173
e462ec50
DH
3174 if (flags & MS_NOUSER)
3175 return -EINVAL;
3176
a1e6aaa3
CH
3177 ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
3178 if (ret)
3179 return ret;
3180 if (!may_mount())
3181 return -EPERM;
3182 if ((flags & SB_MANDLOCK) && !may_mandlock())
3183 return -EPERM;
a27ab9f2 3184
613cbe3d
AK
3185 /* Default to relatime unless overriden */
3186 if (!(flags & MS_NOATIME))
3187 mnt_flags |= MNT_RELATIME;
0a1c01c9 3188
1da177e4
LT
3189 /* Separate the per-mountpoint flags */
3190 if (flags & MS_NOSUID)
3191 mnt_flags |= MNT_NOSUID;
3192 if (flags & MS_NODEV)
3193 mnt_flags |= MNT_NODEV;
3194 if (flags & MS_NOEXEC)
3195 mnt_flags |= MNT_NOEXEC;
fc33a7bb
CH
3196 if (flags & MS_NOATIME)
3197 mnt_flags |= MNT_NOATIME;
3198 if (flags & MS_NODIRATIME)
3199 mnt_flags |= MNT_NODIRATIME;
d0adde57
MG
3200 if (flags & MS_STRICTATIME)
3201 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
a9e5b732 3202 if (flags & MS_RDONLY)
2e4b7fcd 3203 mnt_flags |= MNT_READONLY;
dab741e0
MN
3204 if (flags & MS_NOSYMFOLLOW)
3205 mnt_flags |= MNT_NOSYMFOLLOW;
fc33a7bb 3206
ffbc6f0e
EB
3207 /* The default atime for remount is preservation */
3208 if ((flags & MS_REMOUNT) &&
3209 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3210 MS_STRICTATIME)) == 0)) {
3211 mnt_flags &= ~MNT_ATIME_MASK;
a1e6aaa3 3212 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
ffbc6f0e
EB
3213 }
3214
e462ec50
DH
3215 sb_flags = flags & (SB_RDONLY |
3216 SB_SYNCHRONOUS |
3217 SB_MANDLOCK |
3218 SB_DIRSYNC |
3219 SB_SILENT |
917086ff 3220 SB_POSIXACL |
d7ee9469 3221 SB_LAZYTIME |
917086ff 3222 SB_I_VERSION);
1da177e4 3223
43f5e655 3224 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
a1e6aaa3
CH
3225 return do_reconfigure_mnt(path, mnt_flags);
3226 if (flags & MS_REMOUNT)
3227 return do_remount(path, flags, sb_flags, mnt_flags, data_page);
3228 if (flags & MS_BIND)
3229 return do_loopback(path, dev_name, flags & MS_REC);
3230 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3231 return do_change_type(path, flags);
3232 if (flags & MS_MOVE)
3233 return do_move_mount_old(path, dev_name);
3234
3235 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
3236 data_page);
3237}
3238
3239long do_mount(const char *dev_name, const char __user *dir_name,
3240 const char *type_page, unsigned long flags, void *data_page)
3241{
3242 struct path path;
3243 int ret;
3244
3245 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3246 if (ret)
3247 return ret;
3248 ret = path_mount(dev_name, &path, type_page, flags, data_page);
2d92ab3c 3249 path_put(&path);
a1e6aaa3 3250 return ret;
1da177e4
LT
3251}
3252
537f7ccb
EB
3253static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3254{
3255 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3256}
3257
3258static void dec_mnt_namespaces(struct ucounts *ucounts)
3259{
3260 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3261}
3262
771b1371
EB
3263static void free_mnt_ns(struct mnt_namespace *ns)
3264{
74e83122
AV
3265 if (!is_anon_ns(ns))
3266 ns_free_inum(&ns->ns);
537f7ccb 3267 dec_mnt_namespaces(ns->ucounts);
771b1371
EB
3268 put_user_ns(ns->user_ns);
3269 kfree(ns);
3270}
3271
8823c079
EB
3272/*
3273 * Assign a sequence number so we can detect when we attempt to bind
3274 * mount a reference to an older mount namespace into the current
3275 * mount namespace, preventing reference counting loops. A 64bit
3276 * number incrementing at 10Ghz will take 12,427 years to wrap which
3277 * is effectively never, so we can ignore the possibility.
3278 */
3279static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3280
74e83122 3281static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
cf8d2c11
TM
3282{
3283 struct mnt_namespace *new_ns;
537f7ccb 3284 struct ucounts *ucounts;
98f842e6 3285 int ret;
cf8d2c11 3286
537f7ccb
EB
3287 ucounts = inc_mnt_namespaces(user_ns);
3288 if (!ucounts)
df75e774 3289 return ERR_PTR(-ENOSPC);
537f7ccb 3290
74e83122 3291 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
537f7ccb
EB
3292 if (!new_ns) {
3293 dec_mnt_namespaces(ucounts);
cf8d2c11 3294 return ERR_PTR(-ENOMEM);
537f7ccb 3295 }
74e83122
AV
3296 if (!anon) {
3297 ret = ns_alloc_inum(&new_ns->ns);
3298 if (ret) {
3299 kfree(new_ns);
3300 dec_mnt_namespaces(ucounts);
3301 return ERR_PTR(ret);
3302 }
98f842e6 3303 }
33c42940 3304 new_ns->ns.ops = &mntns_operations;
74e83122
AV
3305 if (!anon)
3306 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
1a7b8969 3307 refcount_set(&new_ns->ns.count, 1);
cf8d2c11
TM
3308 INIT_LIST_HEAD(&new_ns->list);
3309 init_waitqueue_head(&new_ns->poll);
9f6c61f9 3310 spin_lock_init(&new_ns->ns_lock);
771b1371 3311 new_ns->user_ns = get_user_ns(user_ns);
537f7ccb 3312 new_ns->ucounts = ucounts;
cf8d2c11
TM
3313 return new_ns;
3314}
3315
0766f788 3316__latent_entropy
9559f689
AV
3317struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3318 struct user_namespace *user_ns, struct fs_struct *new_fs)
1da177e4 3319{
6b3286ed 3320 struct mnt_namespace *new_ns;
7f2da1e7 3321 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
315fc83e 3322 struct mount *p, *q;
9559f689 3323 struct mount *old;
cb338d06 3324 struct mount *new;
7a472ef4 3325 int copy_flags;
1da177e4 3326
9559f689
AV
3327 BUG_ON(!ns);
3328
3329 if (likely(!(flags & CLONE_NEWNS))) {
3330 get_mnt_ns(ns);
3331 return ns;
3332 }
3333
3334 old = ns->root;
3335
74e83122 3336 new_ns = alloc_mnt_ns(user_ns, false);
cf8d2c11
TM
3337 if (IS_ERR(new_ns))
3338 return new_ns;
1da177e4 3339
97216be0 3340 namespace_lock();
1da177e4 3341 /* First pass: copy the tree topology */
4ce5d2b1 3342 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
9559f689 3343 if (user_ns != ns->user_ns)
3bd045cc 3344 copy_flags |= CL_SHARED_TO_SLAVE;
7a472ef4 3345 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
be34d1a3 3346 if (IS_ERR(new)) {
328e6d90 3347 namespace_unlock();
771b1371 3348 free_mnt_ns(new_ns);
be34d1a3 3349 return ERR_CAST(new);
1da177e4 3350 }
3bd045cc
AV
3351 if (user_ns != ns->user_ns) {
3352 lock_mount_hash();
3353 lock_mnt_tree(new);
3354 unlock_mount_hash();
3355 }
be08d6d2 3356 new_ns->root = new;
1a4eeaf2 3357 list_add_tail(&new_ns->list, &new->mnt_list);
1da177e4
LT
3358
3359 /*
3360 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3361 * as belonging to new namespace. We have already acquired a private
3362 * fs_struct, so tsk->fs->lock is not needed.
3363 */
909b0a88 3364 p = old;
cb338d06 3365 q = new;
1da177e4 3366 while (p) {
143c8c91 3367 q->mnt_ns = new_ns;
d2921684 3368 new_ns->mounts++;
9559f689
AV
3369 if (new_fs) {
3370 if (&p->mnt == new_fs->root.mnt) {
3371 new_fs->root.mnt = mntget(&q->mnt);
315fc83e 3372 rootmnt = &p->mnt;
1da177e4 3373 }
9559f689
AV
3374 if (&p->mnt == new_fs->pwd.mnt) {
3375 new_fs->pwd.mnt = mntget(&q->mnt);
315fc83e 3376 pwdmnt = &p->mnt;
1da177e4 3377 }
1da177e4 3378 }
909b0a88
AV
3379 p = next_mnt(p, old);
3380 q = next_mnt(q, new);
4ce5d2b1
EB
3381 if (!q)
3382 break;
3383 while (p->mnt.mnt_root != q->mnt.mnt_root)
3384 p = next_mnt(p, old);
1da177e4 3385 }
328e6d90 3386 namespace_unlock();
1da177e4 3387
1da177e4 3388 if (rootmnt)
f03c6599 3389 mntput(rootmnt);
1da177e4 3390 if (pwdmnt)
f03c6599 3391 mntput(pwdmnt);
1da177e4 3392
741a2951 3393 return new_ns;
1da177e4
LT
3394}
3395
74e83122 3396struct dentry *mount_subtree(struct vfsmount *m, const char *name)
ea441d11 3397{
74e83122 3398 struct mount *mnt = real_mount(m);
ea441d11 3399 struct mnt_namespace *ns;
d31da0f0 3400 struct super_block *s;
ea441d11
AV
3401 struct path path;
3402 int err;
3403
74e83122
AV
3404 ns = alloc_mnt_ns(&init_user_ns, true);
3405 if (IS_ERR(ns)) {
3406 mntput(m);
ea441d11 3407 return ERR_CAST(ns);
74e83122
AV
3408 }
3409 mnt->mnt_ns = ns;
3410 ns->root = mnt;
3411 ns->mounts++;
3412 list_add(&mnt->mnt_list, &ns->list);
ea441d11 3413
74e83122 3414 err = vfs_path_lookup(m->mnt_root, m,
ea441d11
AV
3415 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3416
3417 put_mnt_ns(ns);
3418
3419 if (err)
3420 return ERR_PTR(err);
3421
3422 /* trade a vfsmount reference for active sb one */
d31da0f0
AV
3423 s = path.mnt->mnt_sb;
3424 atomic_inc(&s->s_active);
ea441d11
AV
3425 mntput(path.mnt);
3426 /* lock the sucker */
d31da0f0 3427 down_write(&s->s_umount);
ea441d11
AV
3428 /* ... and return the root of (sub)tree on it */
3429 return path.dentry;
3430}
3431EXPORT_SYMBOL(mount_subtree);
3432
cccaa5e3
DB
3433SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3434 char __user *, type, unsigned long, flags, void __user *, data)
1da177e4 3435{
eca6f534
VN
3436 int ret;
3437 char *kernel_type;
eca6f534 3438 char *kernel_dev;
b40ef869 3439 void *options;
1da177e4 3440
b8850d1f
TG
3441 kernel_type = copy_mount_string(type);
3442 ret = PTR_ERR(kernel_type);
3443 if (IS_ERR(kernel_type))
eca6f534 3444 goto out_type;
1da177e4 3445
b8850d1f
TG
3446 kernel_dev = copy_mount_string(dev_name);
3447 ret = PTR_ERR(kernel_dev);
3448 if (IS_ERR(kernel_dev))
eca6f534 3449 goto out_dev;
1da177e4 3450
b40ef869
AV
3451 options = copy_mount_options(data);
3452 ret = PTR_ERR(options);
3453 if (IS_ERR(options))
eca6f534 3454 goto out_data;
1da177e4 3455
b40ef869 3456 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
1da177e4 3457
b40ef869 3458 kfree(options);
eca6f534
VN
3459out_data:
3460 kfree(kernel_dev);
3461out_dev:
eca6f534
VN
3462 kfree(kernel_type);
3463out_type:
3464 return ret;
1da177e4
LT
3465}
3466
5b490500
CB
3467#define FSMOUNT_VALID_FLAGS \
3468 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3469 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME)
3470
9caccd41 3471#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
2a186721
CB
3472
3473#define MOUNT_SETATTR_PROPAGATION_FLAGS \
3474 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3475
5b490500
CB
3476static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
3477{
3478 unsigned int mnt_flags = 0;
3479
3480 if (attr_flags & MOUNT_ATTR_RDONLY)
3481 mnt_flags |= MNT_READONLY;
3482 if (attr_flags & MOUNT_ATTR_NOSUID)
3483 mnt_flags |= MNT_NOSUID;
3484 if (attr_flags & MOUNT_ATTR_NODEV)
3485 mnt_flags |= MNT_NODEV;
3486 if (attr_flags & MOUNT_ATTR_NOEXEC)
3487 mnt_flags |= MNT_NOEXEC;
3488 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3489 mnt_flags |= MNT_NODIRATIME;
3490
3491 return mnt_flags;
3492}
3493
2db154b3 3494/*
93766fbd
DH
3495 * Create a kernel mount representation for a new, prepared superblock
3496 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3497 */
3498SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3499 unsigned int, attr_flags)
3500{
3501 struct mnt_namespace *ns;
3502 struct fs_context *fc;
3503 struct file *file;
3504 struct path newmount;
3505 struct mount *mnt;
3506 struct fd f;
3507 unsigned int mnt_flags = 0;
3508 long ret;
3509
3510 if (!may_mount())
3511 return -EPERM;
3512
3513 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3514 return -EINVAL;
3515
5b490500 3516 if (attr_flags & ~FSMOUNT_VALID_FLAGS)
93766fbd
DH
3517 return -EINVAL;
3518
5b490500 3519 mnt_flags = attr_flags_to_mnt_flags(attr_flags);
93766fbd
DH
3520
3521 switch (attr_flags & MOUNT_ATTR__ATIME) {
3522 case MOUNT_ATTR_STRICTATIME:
3523 break;
3524 case MOUNT_ATTR_NOATIME:
3525 mnt_flags |= MNT_NOATIME;
3526 break;
3527 case MOUNT_ATTR_RELATIME:
3528 mnt_flags |= MNT_RELATIME;
3529 break;
3530 default:
3531 return -EINVAL;
3532 }
3533
3534 f = fdget(fs_fd);
3535 if (!f.file)
3536 return -EBADF;
3537
3538 ret = -EINVAL;
3539 if (f.file->f_op != &fscontext_fops)
3540 goto err_fsfd;
3541
3542 fc = f.file->private_data;
3543
3544 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3545 if (ret < 0)
3546 goto err_fsfd;
3547
3548 /* There must be a valid superblock or we can't mount it */
3549 ret = -EINVAL;
3550 if (!fc->root)
3551 goto err_unlock;
3552
3553 ret = -EPERM;
3554 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
3555 pr_warn("VFS: Mount too revealing\n");
3556 goto err_unlock;
3557 }
3558
3559 ret = -EBUSY;
3560 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
3561 goto err_unlock;
3562
3563 ret = -EPERM;
3564 if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock())
3565 goto err_unlock;
3566
3567 newmount.mnt = vfs_create_mount(fc);
3568 if (IS_ERR(newmount.mnt)) {
3569 ret = PTR_ERR(newmount.mnt);
3570 goto err_unlock;
3571 }
3572 newmount.dentry = dget(fc->root);
3573 newmount.mnt->mnt_flags = mnt_flags;
3574
3575 /* We've done the mount bit - now move the file context into more or
3576 * less the same state as if we'd done an fspick(). We don't want to
3577 * do any memory allocation or anything like that at this point as we
3578 * don't want to have to handle any errors incurred.
3579 */
3580 vfs_clean_context(fc);
3581
3582 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
3583 if (IS_ERR(ns)) {
3584 ret = PTR_ERR(ns);
3585 goto err_path;
3586 }
3587 mnt = real_mount(newmount.mnt);
3588 mnt->mnt_ns = ns;
3589 ns->root = mnt;
3590 ns->mounts = 1;
3591 list_add(&mnt->mnt_list, &ns->list);
1b0b9cc8 3592 mntget(newmount.mnt);
93766fbd
DH
3593
3594 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3595 * it, not just simply put it.
3596 */
3597 file = dentry_open(&newmount, O_PATH, fc->cred);
3598 if (IS_ERR(file)) {
3599 dissolve_on_fput(newmount.mnt);
3600 ret = PTR_ERR(file);
3601 goto err_path;
3602 }
3603 file->f_mode |= FMODE_NEED_UNMOUNT;
3604
3605 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
3606 if (ret >= 0)
3607 fd_install(ret, file);
3608 else
3609 fput(file);
3610
3611err_path:
3612 path_put(&newmount);
3613err_unlock:
3614 mutex_unlock(&fc->uapi_mutex);
3615err_fsfd:
3616 fdput(f);
3617 return ret;
3618}
3619
3620/*
3621 * Move a mount from one place to another. In combination with
3622 * fsopen()/fsmount() this is used to install a new mount and in combination
3623 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3624 * a mount subtree.
2db154b3
DH
3625 *
3626 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3627 */
3628SYSCALL_DEFINE5(move_mount,
2658ce09
BD
3629 int, from_dfd, const char __user *, from_pathname,
3630 int, to_dfd, const char __user *, to_pathname,
2db154b3
DH
3631 unsigned int, flags)
3632{
3633 struct path from_path, to_path;
3634 unsigned int lflags;
3635 int ret = 0;
3636
3637 if (!may_mount())
3638 return -EPERM;
3639
3640 if (flags & ~MOVE_MOUNT__MASK)
3641 return -EINVAL;
3642
3643 /* If someone gives a pathname, they aren't permitted to move
3644 * from an fd that requires unmount as we can't get at the flag
3645 * to clear it afterwards.
3646 */
3647 lflags = 0;
3648 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3649 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3650 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3651
3652 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
3653 if (ret < 0)
3654 return ret;
3655
3656 lflags = 0;
3657 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3658 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3659 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3660
3661 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
3662 if (ret < 0)
3663 goto out_from;
3664
3665 ret = security_move_mount(&from_path, &to_path);
3666 if (ret < 0)
3667 goto out_to;
3668
3669 ret = do_move_mount(&from_path, &to_path);
3670
3671out_to:
3672 path_put(&to_path);
3673out_from:
3674 path_put(&from_path);
3675 return ret;
3676}
3677
afac7cba
AV
3678/*
3679 * Return true if path is reachable from root
3680 *
48a066e7 3681 * namespace_sem or mount_lock is held
afac7cba 3682 */
643822b4 3683bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
afac7cba
AV
3684 const struct path *root)
3685{
643822b4 3686 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
a73324da 3687 dentry = mnt->mnt_mountpoint;
0714a533 3688 mnt = mnt->mnt_parent;
afac7cba 3689 }
643822b4 3690 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
afac7cba
AV
3691}
3692
640eb7e7 3693bool path_is_under(const struct path *path1, const struct path *path2)
afac7cba 3694{
25ab4c9b 3695 bool res;
48a066e7 3696 read_seqlock_excl(&mount_lock);
643822b4 3697 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
48a066e7 3698 read_sequnlock_excl(&mount_lock);
afac7cba
AV
3699 return res;
3700}
3701EXPORT_SYMBOL(path_is_under);
3702
1da177e4
LT
3703/*
3704 * pivot_root Semantics:
3705 * Moves the root file system of the current process to the directory put_old,
3706 * makes new_root as the new root file system of the current process, and sets
3707 * root/cwd of all processes which had them on the current root to new_root.
3708 *
3709 * Restrictions:
3710 * The new_root and put_old must be directories, and must not be on the
3711 * same file system as the current process root. The put_old must be
3712 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3713 * pointed to by put_old must yield the same directory as new_root. No other
3714 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3715 *
4a0d11fa 3716 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
0c1bc6b8 3717 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
4a0d11fa
NB
3718 * in this situation.
3719 *
1da177e4
LT
3720 * Notes:
3721 * - we don't move root/cwd if they are not at the root (reason: if something
3722 * cared enough to change them, it's probably wrong to force them elsewhere)
3723 * - it's okay to pick a root that isn't the root of a file system, e.g.
3724 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3725 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3726 * first.
3727 */
3480b257
HC
3728SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3729 const char __user *, put_old)
1da177e4 3730{
2763d119
AV
3731 struct path new, old, root;
3732 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
84d17192 3733 struct mountpoint *old_mp, *root_mp;
1da177e4
LT
3734 int error;
3735
9b40bc90 3736 if (!may_mount())
1da177e4
LT
3737 return -EPERM;
3738
ce6595a2
AV
3739 error = user_path_at(AT_FDCWD, new_root,
3740 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
1da177e4
LT
3741 if (error)
3742 goto out0;
1da177e4 3743
ce6595a2
AV
3744 error = user_path_at(AT_FDCWD, put_old,
3745 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
1da177e4
LT
3746 if (error)
3747 goto out1;
3748
2d8f3038 3749 error = security_sb_pivotroot(&old, &new);
b12cea91
AV
3750 if (error)
3751 goto out2;
1da177e4 3752
f7ad3c6b 3753 get_fs_root(current->fs, &root);
84d17192
AV
3754 old_mp = lock_mount(&old);
3755 error = PTR_ERR(old_mp);
3756 if (IS_ERR(old_mp))
b12cea91
AV
3757 goto out3;
3758
1da177e4 3759 error = -EINVAL;
419148da
AV
3760 new_mnt = real_mount(new.mnt);
3761 root_mnt = real_mount(root.mnt);
84d17192 3762 old_mnt = real_mount(old.mnt);
2763d119
AV
3763 ex_parent = new_mnt->mnt_parent;
3764 root_parent = root_mnt->mnt_parent;
84d17192 3765 if (IS_MNT_SHARED(old_mnt) ||
2763d119
AV
3766 IS_MNT_SHARED(ex_parent) ||
3767 IS_MNT_SHARED(root_parent))
b12cea91 3768 goto out4;
143c8c91 3769 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
b12cea91 3770 goto out4;
5ff9d8a6
EB
3771 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3772 goto out4;
1da177e4 3773 error = -ENOENT;
f3da392e 3774 if (d_unlinked(new.dentry))
b12cea91 3775 goto out4;
1da177e4 3776 error = -EBUSY;
84d17192 3777 if (new_mnt == root_mnt || old_mnt == root_mnt)
b12cea91 3778 goto out4; /* loop, on the same file system */
1da177e4 3779 error = -EINVAL;
8c3ee42e 3780 if (root.mnt->mnt_root != root.dentry)
b12cea91 3781 goto out4; /* not a mountpoint */
676da58d 3782 if (!mnt_has_parent(root_mnt))
b12cea91 3783 goto out4; /* not attached */
2d8f3038 3784 if (new.mnt->mnt_root != new.dentry)
b12cea91 3785 goto out4; /* not a mountpoint */
676da58d 3786 if (!mnt_has_parent(new_mnt))
b12cea91 3787 goto out4; /* not attached */
4ac91378 3788 /* make sure we can reach put_old from new_root */
84d17192 3789 if (!is_path_reachable(old_mnt, old.dentry, &new))
b12cea91 3790 goto out4;
0d082601
EB
3791 /* make certain new is below the root */
3792 if (!is_path_reachable(new_mnt, new.dentry, &root))
3793 goto out4;
719ea2fb 3794 lock_mount_hash();
2763d119
AV
3795 umount_mnt(new_mnt);
3796 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
5ff9d8a6
EB
3797 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3798 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3799 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3800 }
4ac91378 3801 /* mount old root on put_old */
84d17192 3802 attach_mnt(root_mnt, old_mnt, old_mp);
4ac91378 3803 /* mount new_root on / */
2763d119
AV
3804 attach_mnt(new_mnt, root_parent, root_mp);
3805 mnt_add_count(root_parent, -1);
6b3286ed 3806 touch_mnt_namespace(current->nsproxy->mnt_ns);
4fed655c
EB
3807 /* A moved mount should not expire automatically */
3808 list_del_init(&new_mnt->mnt_expire);
3895dbf8 3809 put_mountpoint(root_mp);
719ea2fb 3810 unlock_mount_hash();
2d8f3038 3811 chroot_fs_refs(&root, &new);
1da177e4 3812 error = 0;
b12cea91 3813out4:
84d17192 3814 unlock_mount(old_mp);
2763d119
AV
3815 if (!error)
3816 mntput_no_expire(ex_parent);
b12cea91 3817out3:
8c3ee42e 3818 path_put(&root);
b12cea91 3819out2:
2d8f3038 3820 path_put(&old);
1da177e4 3821out1:
2d8f3038 3822 path_put(&new);
1da177e4 3823out0:
1da177e4 3824 return error;
1da177e4
LT
3825}
3826
2a186721
CB
3827static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
3828{
3829 unsigned int flags = mnt->mnt.mnt_flags;
3830
3831 /* flags to clear */
3832 flags &= ~kattr->attr_clr;
3833 /* flags to raise */
3834 flags |= kattr->attr_set;
3835
3836 return flags;
3837}
3838
9caccd41
CB
3839static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
3840{
3841 struct vfsmount *m = &mnt->mnt;
3842
3843 if (!kattr->mnt_userns)
3844 return 0;
3845
3846 /*
3847 * Once a mount has been idmapped we don't allow it to change its
3848 * mapping. It makes things simpler and callers can just create
3849 * another bind-mount they can idmap if they want to.
3850 */
3851 if (mnt_user_ns(m) != &init_user_ns)
3852 return -EPERM;
3853
3854 /* The underlying filesystem doesn't support idmapped mounts yet. */
3855 if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
3856 return -EINVAL;
3857
3858 /* We're not controlling the superblock. */
3859 if (!ns_capable(m->mnt_sb->s_user_ns, CAP_SYS_ADMIN))
3860 return -EPERM;
3861
3862 /* Mount has already been visible in the filesystem hierarchy. */
3863 if (!is_anon_ns(mnt->mnt_ns))
3864 return -EINVAL;
3865
3866 return 0;
3867}
3868
2a186721
CB
3869static struct mount *mount_setattr_prepare(struct mount_kattr *kattr,
3870 struct mount *mnt, int *err)
3871{
3872 struct mount *m = mnt, *last = NULL;
3873
3874 if (!is_mounted(&m->mnt)) {
3875 *err = -EINVAL;
3876 goto out;
3877 }
3878
3879 if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) {
3880 *err = -EINVAL;
3881 goto out;
3882 }
3883
3884 do {
3885 unsigned int flags;
3886
3887 flags = recalc_flags(kattr, m);
3888 if (!can_change_locked_flags(m, flags)) {
3889 *err = -EPERM;
3890 goto out;
3891 }
3892
9caccd41
CB
3893 *err = can_idmap_mount(kattr, m);
3894 if (*err)
3895 goto out;
3896
2a186721
CB
3897 last = m;
3898
3899 if ((kattr->attr_set & MNT_READONLY) &&
3900 !(m->mnt.mnt_flags & MNT_READONLY)) {
3901 *err = mnt_hold_writers(m);
3902 if (*err)
3903 goto out;
3904 }
3905 } while (kattr->recurse && (m = next_mnt(m, mnt)));
3906
3907out:
3908 return last;
3909}
3910
9caccd41
CB
3911static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
3912{
3913 struct user_namespace *mnt_userns;
3914
3915 if (!kattr->mnt_userns)
3916 return;
3917
3918 mnt_userns = get_user_ns(kattr->mnt_userns);
3919 /* Pairs with smp_load_acquire() in mnt_user_ns(). */
3920 smp_store_release(&mnt->mnt.mnt_userns, mnt_userns);
3921}
3922
2a186721
CB
3923static void mount_setattr_commit(struct mount_kattr *kattr,
3924 struct mount *mnt, struct mount *last,
3925 int err)
3926{
3927 struct mount *m = mnt;
3928
3929 do {
3930 if (!err) {
3931 unsigned int flags;
3932
9caccd41 3933 do_idmap_mount(kattr, m);
2a186721
CB
3934 flags = recalc_flags(kattr, m);
3935 WRITE_ONCE(m->mnt.mnt_flags, flags);
3936 }
3937
3938 /*
3939 * We either set MNT_READONLY above so make it visible
3940 * before ~MNT_WRITE_HOLD or we failed to recursively
3941 * apply mount options.
3942 */
3943 if ((kattr->attr_set & MNT_READONLY) &&
3944 (m->mnt.mnt_flags & MNT_WRITE_HOLD))
3945 mnt_unhold_writers(m);
3946
3947 if (!err && kattr->propagation)
3948 change_mnt_propagation(m, kattr->propagation);
3949
3950 /*
3951 * On failure, only cleanup until we found the first mount
3952 * we failed to handle.
3953 */
3954 if (err && m == last)
3955 break;
3956 } while (kattr->recurse && (m = next_mnt(m, mnt)));
3957
3958 if (!err)
3959 touch_mnt_namespace(mnt->mnt_ns);
3960}
3961
3962static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
3963{
3964 struct mount *mnt = real_mount(path->mnt), *last = NULL;
3965 int err = 0;
3966
3967 if (path->dentry != mnt->mnt.mnt_root)
3968 return -EINVAL;
3969
3970 if (kattr->propagation) {
3971 /*
3972 * Only take namespace_lock() if we're actually changing
3973 * propagation.
3974 */
3975 namespace_lock();
3976 if (kattr->propagation == MS_SHARED) {
3977 err = invent_group_ids(mnt, kattr->recurse);
3978 if (err) {
3979 namespace_unlock();
3980 return err;
3981 }
3982 }
3983 }
3984
3985 lock_mount_hash();
3986
3987 /*
3988 * Get the mount tree in a shape where we can change mount
3989 * properties without failure.
3990 */
3991 last = mount_setattr_prepare(kattr, mnt, &err);
3992 if (last) /* Commit all changes or revert to the old state. */
3993 mount_setattr_commit(kattr, mnt, last, err);
3994
3995 unlock_mount_hash();
3996
3997 if (kattr->propagation) {
3998 namespace_unlock();
3999 if (err)
4000 cleanup_group_ids(mnt, NULL);
4001 }
4002
4003 return err;
4004}
4005
9caccd41
CB
4006static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
4007 struct mount_kattr *kattr, unsigned int flags)
4008{
4009 int err = 0;
4010 struct ns_common *ns;
4011 struct user_namespace *mnt_userns;
4012 struct file *file;
4013
4014 if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
4015 return 0;
4016
4017 /*
4018 * We currently do not support clearing an idmapped mount. If this ever
4019 * is a use-case we can revisit this but for now let's keep it simple
4020 * and not allow it.
4021 */
4022 if (attr->attr_clr & MOUNT_ATTR_IDMAP)
4023 return -EINVAL;
4024
4025 if (attr->userns_fd > INT_MAX)
4026 return -EINVAL;
4027
4028 file = fget(attr->userns_fd);
4029 if (!file)
4030 return -EBADF;
4031
4032 if (!proc_ns_file(file)) {
4033 err = -EINVAL;
4034 goto out_fput;
4035 }
4036
4037 ns = get_proc_ns(file_inode(file));
4038 if (ns->ops->type != CLONE_NEWUSER) {
4039 err = -EINVAL;
4040 goto out_fput;
4041 }
4042
4043 /*
4044 * The init_user_ns is used to indicate that a vfsmount is not idmapped.
4045 * This is simpler than just having to treat NULL as unmapped. Users
4046 * wanting to idmap a mount to init_user_ns can just use a namespace
4047 * with an identity mapping.
4048 */
4049 mnt_userns = container_of(ns, struct user_namespace, ns);
4050 if (mnt_userns == &init_user_ns) {
4051 err = -EPERM;
4052 goto out_fput;
4053 }
4054 kattr->mnt_userns = get_user_ns(mnt_userns);
4055
4056out_fput:
4057 fput(file);
4058 return err;
4059}
4060
4061static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
2a186721
CB
4062 struct mount_kattr *kattr, unsigned int flags)
4063{
4064 unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
4065
4066 if (flags & AT_NO_AUTOMOUNT)
4067 lookup_flags &= ~LOOKUP_AUTOMOUNT;
4068 if (flags & AT_SYMLINK_NOFOLLOW)
4069 lookup_flags &= ~LOOKUP_FOLLOW;
4070 if (flags & AT_EMPTY_PATH)
4071 lookup_flags |= LOOKUP_EMPTY;
4072
4073 *kattr = (struct mount_kattr) {
4074 .lookup_flags = lookup_flags,
4075 .recurse = !!(flags & AT_RECURSIVE),
4076 };
4077
4078 if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
4079 return -EINVAL;
4080 if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
4081 return -EINVAL;
4082 kattr->propagation = attr->propagation;
4083
4084 if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
4085 return -EINVAL;
4086
2a186721
CB
4087 kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
4088 kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
4089
4090 /*
4091 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4092 * users wanting to transition to a different atime setting cannot
4093 * simply specify the atime setting in @attr_set, but must also
4094 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4095 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4096 * @attr_clr and that @attr_set can't have any atime bits set if
4097 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4098 */
4099 if (attr->attr_clr & MOUNT_ATTR__ATIME) {
4100 if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
4101 return -EINVAL;
4102
4103 /*
4104 * Clear all previous time settings as they are mutually
4105 * exclusive.
4106 */
4107 kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
4108 switch (attr->attr_set & MOUNT_ATTR__ATIME) {
4109 case MOUNT_ATTR_RELATIME:
4110 kattr->attr_set |= MNT_RELATIME;
4111 break;
4112 case MOUNT_ATTR_NOATIME:
4113 kattr->attr_set |= MNT_NOATIME;
4114 break;
4115 case MOUNT_ATTR_STRICTATIME:
4116 break;
4117 default:
4118 return -EINVAL;
4119 }
4120 } else {
4121 if (attr->attr_set & MOUNT_ATTR__ATIME)
4122 return -EINVAL;
4123 }
4124
9caccd41
CB
4125 return build_mount_idmapped(attr, usize, kattr, flags);
4126}
4127
4128static void finish_mount_kattr(struct mount_kattr *kattr)
4129{
4130 put_user_ns(kattr->mnt_userns);
4131 kattr->mnt_userns = NULL;
2a186721
CB
4132}
4133
4134SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
4135 unsigned int, flags, struct mount_attr __user *, uattr,
4136 size_t, usize)
4137{
4138 int err;
4139 struct path target;
4140 struct mount_attr attr;
4141 struct mount_kattr kattr;
4142
4143 BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
4144
4145 if (flags & ~(AT_EMPTY_PATH |
4146 AT_RECURSIVE |
4147 AT_SYMLINK_NOFOLLOW |
4148 AT_NO_AUTOMOUNT))
4149 return -EINVAL;
4150
4151 if (unlikely(usize > PAGE_SIZE))
4152 return -E2BIG;
4153 if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
4154 return -EINVAL;
4155
4156 if (!may_mount())
4157 return -EPERM;
4158
4159 err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
4160 if (err)
4161 return err;
4162
4163 /* Don't bother walking through the mounts if this is a nop. */
4164 if (attr.attr_set == 0 &&
4165 attr.attr_clr == 0 &&
4166 attr.propagation == 0)
4167 return 0;
4168
9caccd41 4169 err = build_mount_kattr(&attr, usize, &kattr, flags);
2a186721
CB
4170 if (err)
4171 return err;
4172
4173 err = user_path_at(dfd, path, kattr.lookup_flags, &target);
4174 if (err)
4175 return err;
4176
4177 err = do_mount_setattr(&target, &kattr);
9caccd41 4178 finish_mount_kattr(&kattr);
2a186721
CB
4179 path_put(&target);
4180 return err;
4181}
4182
1da177e4
LT
4183static void __init init_mount_tree(void)
4184{
4185 struct vfsmount *mnt;
74e83122 4186 struct mount *m;
6b3286ed 4187 struct mnt_namespace *ns;
ac748a09 4188 struct path root;
1da177e4 4189
fd3e007f 4190 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
1da177e4
LT
4191 if (IS_ERR(mnt))
4192 panic("Can't create rootfs");
b3e19d92 4193
74e83122 4194 ns = alloc_mnt_ns(&init_user_ns, false);
3b22edc5 4195 if (IS_ERR(ns))
1da177e4 4196 panic("Can't allocate initial namespace");
74e83122
AV
4197 m = real_mount(mnt);
4198 m->mnt_ns = ns;
4199 ns->root = m;
4200 ns->mounts = 1;
4201 list_add(&m->mnt_list, &ns->list);
6b3286ed
KK
4202 init_task.nsproxy->mnt_ns = ns;
4203 get_mnt_ns(ns);
4204
be08d6d2
AV
4205 root.mnt = mnt;
4206 root.dentry = mnt->mnt_root;
da362b09 4207 mnt->mnt_flags |= MNT_LOCKED;
ac748a09
JB
4208
4209 set_fs_pwd(current->fs, &root);
4210 set_fs_root(current->fs, &root);
1da177e4
LT
4211}
4212
74bf17cf 4213void __init mnt_init(void)
1da177e4 4214{
15a67dd8 4215 int err;
1da177e4 4216
7d6fec45 4217 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
20c2df83 4218 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
1da177e4 4219
0818bf27 4220 mount_hashtable = alloc_large_system_hash("Mount-cache",
38129a13 4221 sizeof(struct hlist_head),
0818bf27 4222 mhash_entries, 19,
3d375d78 4223 HASH_ZERO,
0818bf27
AV
4224 &m_hash_shift, &m_hash_mask, 0, 0);
4225 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
4226 sizeof(struct hlist_head),
4227 mphash_entries, 19,
3d375d78 4228 HASH_ZERO,
0818bf27 4229 &mp_hash_shift, &mp_hash_mask, 0, 0);
1da177e4 4230
84d17192 4231 if (!mount_hashtable || !mountpoint_hashtable)
1da177e4
LT
4232 panic("Failed to allocate mount hash table\n");
4233
4b93dc9b
TH
4234 kernfs_init();
4235
15a67dd8
RD
4236 err = sysfs_init();
4237 if (err)
4238 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
8e24eea7 4239 __func__, err);
00d26666
GKH
4240 fs_kobj = kobject_create_and_add("fs", NULL);
4241 if (!fs_kobj)
8e24eea7 4242 printk(KERN_WARNING "%s: kobj create error\n", __func__);
037f11b4 4243 shmem_init();
1da177e4
LT
4244 init_rootfs();
4245 init_mount_tree();
4246}
4247
616511d0 4248void put_mnt_ns(struct mnt_namespace *ns)
1da177e4 4249{
1a7b8969 4250 if (!refcount_dec_and_test(&ns->ns.count))
616511d0 4251 return;
7b00ed6f 4252 drop_collected_mounts(&ns->root->mnt);
771b1371 4253 free_mnt_ns(ns);
1da177e4 4254}
9d412a43 4255
d911b458 4256struct vfsmount *kern_mount(struct file_system_type *type)
9d412a43 4257{
423e0ab0 4258 struct vfsmount *mnt;
d911b458 4259 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
423e0ab0
TC
4260 if (!IS_ERR(mnt)) {
4261 /*
4262 * it is a longterm mount, don't release mnt until
4263 * we unmount before file sys is unregistered
4264 */
f7a99c5b 4265 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
423e0ab0
TC
4266 }
4267 return mnt;
9d412a43 4268}
d911b458 4269EXPORT_SYMBOL_GPL(kern_mount);
423e0ab0
TC
4270
4271void kern_unmount(struct vfsmount *mnt)
4272{
4273 /* release long term mount so mount point can be released */
4274 if (!IS_ERR_OR_NULL(mnt)) {
f7a99c5b 4275 real_mount(mnt)->mnt_ns = NULL;
48a066e7 4276 synchronize_rcu(); /* yecchhh... */
423e0ab0
TC
4277 mntput(mnt);
4278 }
4279}
4280EXPORT_SYMBOL(kern_unmount);
02125a82 4281
df820f8d
MS
4282void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
4283{
4284 unsigned int i;
4285
4286 for (i = 0; i < num; i++)
4287 if (mnt[i])
4288 real_mount(mnt[i])->mnt_ns = NULL;
4289 synchronize_rcu_expedited();
4290 for (i = 0; i < num; i++)
4291 mntput(mnt[i]);
4292}
4293EXPORT_SYMBOL(kern_unmount_array);
4294
02125a82
AV
4295bool our_mnt(struct vfsmount *mnt)
4296{
143c8c91 4297 return check_mnt(real_mount(mnt));
02125a82 4298}
8823c079 4299
3151527e
EB
4300bool current_chrooted(void)
4301{
4302 /* Does the current process have a non-standard root */
4303 struct path ns_root;
4304 struct path fs_root;
4305 bool chrooted;
4306
4307 /* Find the namespace root */
4308 ns_root.mnt = &current->nsproxy->mnt_ns->root->mnt;
4309 ns_root.dentry = ns_root.mnt->mnt_root;
4310 path_get(&ns_root);
4311 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
4312 ;
4313
4314 get_fs_root(current->fs, &fs_root);
4315
4316 chrooted = !path_equal(&fs_root, &ns_root);
4317
4318 path_put(&fs_root);
4319 path_put(&ns_root);
4320
4321 return chrooted;
4322}
4323
132e4608
DH
4324static bool mnt_already_visible(struct mnt_namespace *ns,
4325 const struct super_block *sb,
8654df4e 4326 int *new_mnt_flags)
87a8ebd6 4327{
8c6cf9cc 4328 int new_flags = *new_mnt_flags;
87a8ebd6 4329 struct mount *mnt;
e51db735 4330 bool visible = false;
87a8ebd6 4331
44bb4385 4332 down_read(&namespace_sem);
9f6c61f9 4333 lock_ns_list(ns);
87a8ebd6 4334 list_for_each_entry(mnt, &ns->list, mnt_list) {
e51db735 4335 struct mount *child;
77b1a97d
EB
4336 int mnt_flags;
4337
9f6c61f9
MS
4338 if (mnt_is_cursor(mnt))
4339 continue;
4340
132e4608 4341 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
e51db735
EB
4342 continue;
4343
7e96c1b0
EB
4344 /* This mount is not fully visible if it's root directory
4345 * is not the root directory of the filesystem.
4346 */
4347 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
4348 continue;
4349
a1935c17 4350 /* A local view of the mount flags */
77b1a97d 4351 mnt_flags = mnt->mnt.mnt_flags;
77b1a97d 4352
695e9df0 4353 /* Don't miss readonly hidden in the superblock flags */
bc98a42c 4354 if (sb_rdonly(mnt->mnt.mnt_sb))
695e9df0
EB
4355 mnt_flags |= MNT_LOCK_READONLY;
4356
8c6cf9cc
EB
4357 /* Verify the mount flags are equal to or more permissive
4358 * than the proposed new mount.
4359 */
77b1a97d 4360 if ((mnt_flags & MNT_LOCK_READONLY) &&
8c6cf9cc
EB
4361 !(new_flags & MNT_READONLY))
4362 continue;
77b1a97d
EB
4363 if ((mnt_flags & MNT_LOCK_ATIME) &&
4364 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
8c6cf9cc
EB
4365 continue;
4366
ceeb0e5d
EB
4367 /* This mount is not fully visible if there are any
4368 * locked child mounts that cover anything except for
4369 * empty directories.
e51db735
EB
4370 */
4371 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
4372 struct inode *inode = child->mnt_mountpoint->d_inode;
ceeb0e5d 4373 /* Only worry about locked mounts */
d71ed6c9 4374 if (!(child->mnt.mnt_flags & MNT_LOCKED))
ceeb0e5d 4375 continue;
7236c85e
EB
4376 /* Is the directory permanetly empty? */
4377 if (!is_empty_dir_inode(inode))
e51db735 4378 goto next;
87a8ebd6 4379 }
8c6cf9cc 4380 /* Preserve the locked attributes */
77b1a97d 4381 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
77b1a97d 4382 MNT_LOCK_ATIME);
e51db735
EB
4383 visible = true;
4384 goto found;
4385 next: ;
87a8ebd6 4386 }
e51db735 4387found:
9f6c61f9 4388 unlock_ns_list(ns);
44bb4385 4389 up_read(&namespace_sem);
e51db735 4390 return visible;
87a8ebd6
EB
4391}
4392
132e4608 4393static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
8654df4e 4394{
a1935c17 4395 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
8654df4e
EB
4396 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
4397 unsigned long s_iflags;
4398
4399 if (ns->user_ns == &init_user_ns)
4400 return false;
4401
4402 /* Can this filesystem be too revealing? */
132e4608 4403 s_iflags = sb->s_iflags;
8654df4e
EB
4404 if (!(s_iflags & SB_I_USERNS_VISIBLE))
4405 return false;
4406
a1935c17
EB
4407 if ((s_iflags & required_iflags) != required_iflags) {
4408 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4409 required_iflags);
4410 return true;
4411 }
4412
132e4608 4413 return !mnt_already_visible(ns, sb, new_mnt_flags);
8654df4e
EB
4414}
4415
380cf5ba
AL
4416bool mnt_may_suid(struct vfsmount *mnt)
4417{
4418 /*
4419 * Foreign mounts (accessed via fchdir or through /proc
4420 * symlinks) are always treated as if they are nosuid. This
4421 * prevents namespaces from trusting potentially unsafe
4422 * suid/sgid bits, file caps, or security labels that originate
4423 * in other namespaces.
4424 */
4425 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
4426 current_in_userns(mnt->mnt_sb->s_user_ns);
4427}
4428
64964528 4429static struct ns_common *mntns_get(struct task_struct *task)
8823c079 4430{
58be2825 4431 struct ns_common *ns = NULL;
8823c079
EB
4432 struct nsproxy *nsproxy;
4433
728dba3a
EB
4434 task_lock(task);
4435 nsproxy = task->nsproxy;
8823c079 4436 if (nsproxy) {
58be2825
AV
4437 ns = &nsproxy->mnt_ns->ns;
4438 get_mnt_ns(to_mnt_ns(ns));
8823c079 4439 }
728dba3a 4440 task_unlock(task);
8823c079
EB
4441
4442 return ns;
4443}
4444
64964528 4445static void mntns_put(struct ns_common *ns)
8823c079 4446{
58be2825 4447 put_mnt_ns(to_mnt_ns(ns));
8823c079
EB
4448}
4449
f2a8d52e 4450static int mntns_install(struct nsset *nsset, struct ns_common *ns)
8823c079 4451{
f2a8d52e
CB
4452 struct nsproxy *nsproxy = nsset->nsproxy;
4453 struct fs_struct *fs = nsset->fs;
4f757f3c 4454 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
f2a8d52e 4455 struct user_namespace *user_ns = nsset->cred->user_ns;
8823c079 4456 struct path root;
4f757f3c 4457 int err;
8823c079 4458
0c55cfc4 4459 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
f2a8d52e
CB
4460 !ns_capable(user_ns, CAP_SYS_CHROOT) ||
4461 !ns_capable(user_ns, CAP_SYS_ADMIN))
ae11e0f1 4462 return -EPERM;
8823c079 4463
74e83122
AV
4464 if (is_anon_ns(mnt_ns))
4465 return -EINVAL;
4466
8823c079
EB
4467 if (fs->users != 1)
4468 return -EINVAL;
4469
4470 get_mnt_ns(mnt_ns);
4f757f3c 4471 old_mnt_ns = nsproxy->mnt_ns;
8823c079
EB
4472 nsproxy->mnt_ns = mnt_ns;
4473
4474 /* Find the root */
4f757f3c
AV
4475 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
4476 "/", LOOKUP_DOWN, &root);
4477 if (err) {
4478 /* revert to old namespace */
4479 nsproxy->mnt_ns = old_mnt_ns;
4480 put_mnt_ns(mnt_ns);
4481 return err;
4482 }
8823c079 4483
4068367c
AV
4484 put_mnt_ns(old_mnt_ns);
4485
8823c079
EB
4486 /* Update the pwd and root */
4487 set_fs_pwd(fs, &root);
4488 set_fs_root(fs, &root);
4489
4490 path_put(&root);
4491 return 0;
4492}
4493
bcac25a5
AV
4494static struct user_namespace *mntns_owner(struct ns_common *ns)
4495{
4496 return to_mnt_ns(ns)->user_ns;
4497}
4498
8823c079
EB
4499const struct proc_ns_operations mntns_operations = {
4500 .name = "mnt",
4501 .type = CLONE_NEWNS,
4502 .get = mntns_get,
4503 .put = mntns_put,
4504 .install = mntns_install,
bcac25a5 4505 .owner = mntns_owner,
8823c079 4506};