1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/fs/file_table.c
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
9 #include <linux/string.h>
10 #include <linux/slab.h>
11 #include <linux/file.h>
12 #include <linux/fdtable.h>
13 #include <linux/init.h>
14 #include <linux/module.h>
16 #include <linux/security.h>
17 #include <linux/cred.h>
18 #include <linux/eventpoll.h>
19 #include <linux/rcupdate.h>
20 #include <linux/mount.h>
21 #include <linux/capability.h>
22 #include <linux/cdev.h>
23 #include <linux/fsnotify.h>
24 #include <linux/sysctl.h>
25 #include <linux/percpu_counter.h>
26 #include <linux/percpu.h>
27 #include <linux/task_work.h>
28 #include <linux/ima.h>
29 #include <linux/swap.h>
30 #include <linux/kmemleak.h>
32 #include <linux/atomic.h>
36 /* sysctl tunables... */
37 static struct files_stat_struct files_stat
= {
41 /* SLAB cache for file structures */
42 static struct kmem_cache
*filp_cachep __read_mostly
;
44 static struct percpu_counter nr_files __cacheline_aligned_in_smp
;
46 static void file_free_rcu(struct rcu_head
*head
)
48 struct file
*f
= container_of(head
, struct file
, f_rcuhead
);
51 kmem_cache_free(filp_cachep
, f
);
54 static inline void file_free(struct file
*f
)
56 security_file_free(f
);
57 if (!(f
->f_mode
& FMODE_NOACCOUNT
))
58 percpu_counter_dec(&nr_files
);
59 call_rcu(&f
->f_rcuhead
, file_free_rcu
);
63 * Return the total number of open files in the system
65 static long get_nr_files(void)
67 return percpu_counter_read_positive(&nr_files
);
71 * Return the maximum number of open files in the system
73 unsigned long get_max_files(void)
75 return files_stat
.max_files
;
77 EXPORT_SYMBOL_GPL(get_max_files
);
79 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
82 * Handle nr_files sysctl
84 static int proc_nr_files(struct ctl_table
*table
, int write
, void *buffer
,
85 size_t *lenp
, loff_t
*ppos
)
87 files_stat
.nr_files
= get_nr_files();
88 return proc_doulongvec_minmax(table
, write
, buffer
, lenp
, ppos
);
91 static struct ctl_table fs_stat_sysctls
[] = {
93 .procname
= "file-nr",
95 .maxlen
= sizeof(files_stat
),
97 .proc_handler
= proc_nr_files
,
100 .procname
= "file-max",
101 .data
= &files_stat
.max_files
,
102 .maxlen
= sizeof(files_stat
.max_files
),
104 .proc_handler
= proc_doulongvec_minmax
,
105 .extra1
= SYSCTL_LONG_ZERO
,
106 .extra2
= SYSCTL_LONG_MAX
,
109 .procname
= "nr_open",
110 .data
= &sysctl_nr_open
,
111 .maxlen
= sizeof(unsigned int),
113 .proc_handler
= proc_dointvec_minmax
,
114 .extra1
= &sysctl_nr_open_min
,
115 .extra2
= &sysctl_nr_open_max
,
120 static int __init
init_fs_stat_sysctls(void)
122 register_sysctl_init("fs", fs_stat_sysctls
);
123 if (IS_ENABLED(CONFIG_BINFMT_MISC
)) {
124 struct ctl_table_header
*hdr
;
125 hdr
= register_sysctl_mount_point("fs/binfmt_misc");
126 kmemleak_not_leak(hdr
);
130 fs_initcall(init_fs_stat_sysctls
);
133 static struct file
*__alloc_file(int flags
, const struct cred
*cred
)
138 f
= kmem_cache_zalloc(filp_cachep
, GFP_KERNEL
);
140 return ERR_PTR(-ENOMEM
);
142 f
->f_cred
= get_cred(cred
);
143 error
= security_file_alloc(f
);
144 if (unlikely(error
)) {
145 file_free_rcu(&f
->f_rcuhead
);
146 return ERR_PTR(error
);
149 atomic_long_set(&f
->f_count
, 1);
150 rwlock_init(&f
->f_owner
.lock
);
151 spin_lock_init(&f
->f_lock
);
152 mutex_init(&f
->f_pos_lock
);
154 f
->f_mode
= OPEN_FMODE(flags
);
155 /* f->f_version: 0 */
160 /* Find an unused file structure and return a pointer to it.
161 * Returns an error pointer if some error happend e.g. we over file
162 * structures limit, run out of memory or operation is not permitted.
164 * Be very careful using this. You are responsible for
165 * getting write access to any mount that you might assign
166 * to this filp, if it is opened for write. If this is not
167 * done, you will imbalance int the mount's writer count
168 * and a warning at __fput() time.
170 struct file
*alloc_empty_file(int flags
, const struct cred
*cred
)
176 * Privileged users can go above max_files
178 if (get_nr_files() >= files_stat
.max_files
&& !capable(CAP_SYS_ADMIN
)) {
180 * percpu_counters are inaccurate. Do an expensive check before
183 if (percpu_counter_sum_positive(&nr_files
) >= files_stat
.max_files
)
187 f
= __alloc_file(flags
, cred
);
189 percpu_counter_inc(&nr_files
);
194 /* Ran out of filps - report that */
195 if (get_nr_files() > old_max
) {
196 pr_info("VFS: file-max limit %lu reached\n", get_max_files());
197 old_max
= get_nr_files();
199 return ERR_PTR(-ENFILE
);
203 * Variant of alloc_empty_file() that doesn't check and modify nr_files.
205 * Should not be used unless there's a very good reason to do so.
207 struct file
*alloc_empty_file_noaccount(int flags
, const struct cred
*cred
)
209 struct file
*f
= __alloc_file(flags
, cred
);
212 f
->f_mode
|= FMODE_NOACCOUNT
;
218 * alloc_file - allocate and initialize a 'struct file'
220 * @path: the (dentry, vfsmount) pair for the new file
221 * @flags: O_... flags with which the new file will be opened
222 * @fop: the 'struct file_operations' for the new file
224 static struct file
*alloc_file(const struct path
*path
, int flags
,
225 const struct file_operations
*fop
)
229 file
= alloc_empty_file(flags
, current_cred());
233 file
->f_path
= *path
;
234 file
->f_inode
= path
->dentry
->d_inode
;
235 file
->f_mapping
= path
->dentry
->d_inode
->i_mapping
;
236 file
->f_wb_err
= filemap_sample_wb_err(file
->f_mapping
);
237 file
->f_sb_err
= file_sample_sb_err(file
);
239 file
->f_mode
|= FMODE_LSEEK
;
240 if ((file
->f_mode
& FMODE_READ
) &&
241 likely(fop
->read
|| fop
->read_iter
))
242 file
->f_mode
|= FMODE_CAN_READ
;
243 if ((file
->f_mode
& FMODE_WRITE
) &&
244 likely(fop
->write
|| fop
->write_iter
))
245 file
->f_mode
|= FMODE_CAN_WRITE
;
246 file
->f_iocb_flags
= iocb_flags(file
);
247 file
->f_mode
|= FMODE_OPENED
;
249 if ((file
->f_mode
& (FMODE_READ
| FMODE_WRITE
)) == FMODE_READ
)
250 i_readcount_inc(path
->dentry
->d_inode
);
254 struct file
*alloc_file_pseudo(struct inode
*inode
, struct vfsmount
*mnt
,
255 const char *name
, int flags
,
256 const struct file_operations
*fops
)
258 static const struct dentry_operations anon_ops
= {
259 .d_dname
= simple_dname
261 struct qstr
this = QSTR_INIT(name
, strlen(name
));
265 path
.dentry
= d_alloc_pseudo(mnt
->mnt_sb
, &this);
267 return ERR_PTR(-ENOMEM
);
268 if (!mnt
->mnt_sb
->s_d_op
)
269 d_set_d_op(path
.dentry
, &anon_ops
);
270 path
.mnt
= mntget(mnt
);
271 d_instantiate(path
.dentry
, inode
);
272 file
= alloc_file(&path
, flags
, fops
);
279 EXPORT_SYMBOL(alloc_file_pseudo
);
281 struct file
*alloc_file_clone(struct file
*base
, int flags
,
282 const struct file_operations
*fops
)
284 struct file
*f
= alloc_file(&base
->f_path
, flags
, fops
);
286 path_get(&f
->f_path
);
287 f
->f_mapping
= base
->f_mapping
;
292 /* the real guts of fput() - releasing the last reference to file
294 static void __fput(struct file
*file
)
296 struct dentry
*dentry
= file
->f_path
.dentry
;
297 struct vfsmount
*mnt
= file
->f_path
.mnt
;
298 struct inode
*inode
= file
->f_inode
;
299 fmode_t mode
= file
->f_mode
;
301 if (unlikely(!(file
->f_mode
& FMODE_OPENED
)))
306 fsnotify_close(file
);
308 * The function eventpoll_release() should be the first called
309 * in the file cleanup chain.
311 eventpoll_release(file
);
312 locks_remove_file(file
);
315 if (unlikely(file
->f_flags
& FASYNC
)) {
316 if (file
->f_op
->fasync
)
317 file
->f_op
->fasync(-1, file
, 0);
319 if (file
->f_op
->release
)
320 file
->f_op
->release(inode
, file
);
321 if (unlikely(S_ISCHR(inode
->i_mode
) && inode
->i_cdev
!= NULL
&&
322 !(mode
& FMODE_PATH
))) {
323 cdev_put(inode
->i_cdev
);
325 fops_put(file
->f_op
);
326 put_pid(file
->f_owner
.pid
);
327 if ((mode
& (FMODE_READ
| FMODE_WRITE
)) == FMODE_READ
)
328 i_readcount_dec(inode
);
329 if (mode
& FMODE_WRITER
) {
330 put_write_access(inode
);
331 __mnt_drop_write(mnt
);
334 if (unlikely(mode
& FMODE_NEED_UNMOUNT
))
335 dissolve_on_fput(mnt
);
341 static LLIST_HEAD(delayed_fput_list
);
342 static void delayed_fput(struct work_struct
*unused
)
344 struct llist_node
*node
= llist_del_all(&delayed_fput_list
);
347 llist_for_each_entry_safe(f
, t
, node
, f_llist
)
351 static void ____fput(struct callback_head
*work
)
353 __fput(container_of(work
, struct file
, f_rcuhead
));
357 * If kernel thread really needs to have the final fput() it has done
358 * to complete, call this. The only user right now is the boot - we
359 * *do* need to make sure our writes to binaries on initramfs has
360 * not left us with opened struct file waiting for __fput() - execve()
361 * won't work without that. Please, don't add more callers without
362 * very good reasons; in particular, never call that with locks
363 * held and never call that from a thread that might need to do
364 * some work on any kind of umount.
366 void flush_delayed_fput(void)
370 EXPORT_SYMBOL_GPL(flush_delayed_fput
);
372 static DECLARE_DELAYED_WORK(delayed_fput_work
, delayed_fput
);
374 void fput(struct file
*file
)
376 if (atomic_long_dec_and_test(&file
->f_count
)) {
377 struct task_struct
*task
= current
;
379 if (likely(!in_interrupt() && !(task
->flags
& PF_KTHREAD
))) {
380 init_task_work(&file
->f_rcuhead
, ____fput
);
381 if (!task_work_add(task
, &file
->f_rcuhead
, TWA_RESUME
))
384 * After this task has run exit_task_work(),
385 * task_work_add() will fail. Fall through to delayed
386 * fput to avoid leaking *file.
390 if (llist_add(&file
->f_llist
, &delayed_fput_list
))
391 schedule_delayed_work(&delayed_fput_work
, 1);
396 * synchronous analog of fput(); for kernel threads that might be needed
397 * in some umount() (and thus can't use flush_delayed_fput() without
398 * risking deadlocks), need to wait for completion of __fput() and know
399 * for this specific struct file it won't involve anything that would
400 * need them. Use only if you really need it - at the very least,
401 * don't blindly convert fput() by kernel thread to that.
403 void __fput_sync(struct file
*file
)
405 if (atomic_long_dec_and_test(&file
->f_count
)) {
406 struct task_struct
*task
= current
;
407 BUG_ON(!(task
->flags
& PF_KTHREAD
));
413 EXPORT_SYMBOL(__fput_sync
);
415 void __init
files_init(void)
417 filp_cachep
= kmem_cache_create("filp", sizeof(struct file
), 0,
418 SLAB_HWCACHE_ALIGN
| SLAB_PANIC
| SLAB_ACCOUNT
, NULL
);
419 percpu_counter_init(&nr_files
, 0, GFP_KERNEL
);
423 * One file with associated inode and dcache is very roughly 1K. Per default
424 * do not use more than 10% of our memory for files.
426 void __init
files_maxfiles_init(void)
429 unsigned long nr_pages
= totalram_pages();
430 unsigned long memreserve
= (nr_pages
- nr_free_pages()) * 3/2;
432 memreserve
= min(memreserve
, nr_pages
- 1);
433 n
= ((nr_pages
- memreserve
) * (PAGE_SIZE
/ 1024)) / 10;
435 files_stat
.max_files
= max_t(unsigned long, n
, NR_FILE
);