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Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
2b2af54a KS |
2 | /* |
3 | * devtmpfs - kernel-maintained tmpfs-based /dev | |
4 | * | |
5 | * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org> | |
6 | * | |
7 | * During bootup, before any driver core device is registered, | |
8 | * devtmpfs, a tmpfs-based filesystem is created. Every driver-core | |
9 | * device which requests a device node, will add a node in this | |
e454cea2 | 10 | * filesystem. |
02fbe5e6 PK |
11 | * By default, all devices are named after the name of the device, |
12 | * owned by root and have a default mode of 0600. Subsystems can | |
13 | * overwrite the default setting if needed. | |
2b2af54a KS |
14 | */ |
15 | ||
16 | #include <linux/kernel.h> | |
17 | #include <linux/syscalls.h> | |
18 | #include <linux/mount.h> | |
19 | #include <linux/device.h> | |
20 | #include <linux/genhd.h> | |
21 | #include <linux/namei.h> | |
22 | #include <linux/fs.h> | |
23 | #include <linux/shmem_fs.h> | |
da5e4ef7 | 24 | #include <linux/ramfs.h> |
e454cea2 | 25 | #include <linux/sched.h> |
5a0e3ad6 | 26 | #include <linux/slab.h> |
2780f1ff | 27 | #include <linux/kthread.h> |
c60166f0 | 28 | #include <linux/init_syscalls.h> |
e262e32d | 29 | #include <uapi/linux/mount.h> |
c3a30420 | 30 | #include "base.h" |
2b2af54a | 31 | |
2780f1ff | 32 | static struct task_struct *thread; |
2b2af54a | 33 | |
fad1db8a | 34 | static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT); |
2b2af54a | 35 | |
2780f1ff AV |
36 | static DEFINE_SPINLOCK(req_lock); |
37 | ||
38 | static struct req { | |
39 | struct req *next; | |
40 | struct completion done; | |
41 | int err; | |
42 | const char *name; | |
2c9ede55 | 43 | umode_t mode; /* 0 => delete */ |
4e4098a3 GKH |
44 | kuid_t uid; |
45 | kgid_t gid; | |
2780f1ff AV |
46 | struct device *dev; |
47 | } *requests; | |
ed413ae6 | 48 | |
2b2af54a KS |
49 | static int __init mount_param(char *str) |
50 | { | |
fc14f2fe | 51 | mount_dev = simple_strtoul(str, NULL, 0); |
2b2af54a KS |
52 | return 1; |
53 | } | |
54 | __setup("devtmpfs.mount=", mount_param); | |
55 | ||
d401727e AV |
56 | static struct vfsmount *mnt; |
57 | ||
58 | static struct dentry *public_dev_mount(struct file_system_type *fs_type, int flags, | |
59 | const char *dev_name, void *data) | |
60 | { | |
61 | struct super_block *s = mnt->mnt_sb; | |
62 | atomic_inc(&s->s_active); | |
63 | down_write(&s->s_umount); | |
64 | return dget(s->s_root); | |
65 | } | |
66 | ||
f3235626 DH |
67 | static struct file_system_type internal_fs_type = { |
68 | .name = "devtmpfs", | |
da5e4ef7 | 69 | #ifdef CONFIG_TMPFS |
f3235626 | 70 | .init_fs_context = shmem_init_fs_context, |
d7167b14 | 71 | .parameters = shmem_fs_parameters, |
da5e4ef7 | 72 | #else |
f3235626 | 73 | .init_fs_context = ramfs_init_fs_context, |
d7167b14 | 74 | .parameters = ramfs_fs_parameters, |
da5e4ef7 | 75 | #endif |
2b2af54a KS |
76 | .kill_sb = kill_litter_super, |
77 | }; | |
78 | ||
d401727e AV |
79 | static struct file_system_type dev_fs_type = { |
80 | .name = "devtmpfs", | |
81 | .mount = public_dev_mount, | |
82 | }; | |
83 | ||
2b2af54a KS |
84 | #ifdef CONFIG_BLOCK |
85 | static inline int is_blockdev(struct device *dev) | |
86 | { | |
87 | return dev->class == &block_class; | |
88 | } | |
89 | #else | |
90 | static inline int is_blockdev(struct device *dev) { return 0; } | |
91 | #endif | |
92 | ||
72a9cc95 RV |
93 | static int devtmpfs_submit_req(struct req *req, const char *tmp) |
94 | { | |
95 | init_completion(&req->done); | |
96 | ||
97 | spin_lock(&req_lock); | |
98 | req->next = requests; | |
99 | requests = req; | |
100 | spin_unlock(&req_lock); | |
101 | ||
102 | wake_up_process(thread); | |
103 | wait_for_completion(&req->done); | |
104 | ||
105 | kfree(tmp); | |
106 | ||
107 | return req->err; | |
108 | } | |
109 | ||
2780f1ff AV |
110 | int devtmpfs_create_node(struct device *dev) |
111 | { | |
112 | const char *tmp = NULL; | |
113 | struct req req; | |
114 | ||
115 | if (!thread) | |
116 | return 0; | |
117 | ||
118 | req.mode = 0; | |
4e4098a3 GKH |
119 | req.uid = GLOBAL_ROOT_UID; |
120 | req.gid = GLOBAL_ROOT_GID; | |
3c2670e6 | 121 | req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp); |
2780f1ff AV |
122 | if (!req.name) |
123 | return -ENOMEM; | |
124 | ||
125 | if (req.mode == 0) | |
126 | req.mode = 0600; | |
127 | if (is_blockdev(dev)) | |
128 | req.mode |= S_IFBLK; | |
129 | else | |
130 | req.mode |= S_IFCHR; | |
131 | ||
132 | req.dev = dev; | |
133 | ||
72a9cc95 | 134 | return devtmpfs_submit_req(&req, tmp); |
2780f1ff AV |
135 | } |
136 | ||
137 | int devtmpfs_delete_node(struct device *dev) | |
138 | { | |
139 | const char *tmp = NULL; | |
140 | struct req req; | |
141 | ||
142 | if (!thread) | |
143 | return 0; | |
144 | ||
3c2670e6 | 145 | req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp); |
2780f1ff AV |
146 | if (!req.name) |
147 | return -ENOMEM; | |
148 | ||
149 | req.mode = 0; | |
150 | req.dev = dev; | |
151 | ||
72a9cc95 | 152 | return devtmpfs_submit_req(&req, tmp); |
2780f1ff AV |
153 | } |
154 | ||
fbd48a69 | 155 | static int dev_mkdir(const char *name, umode_t mode) |
2b2af54a | 156 | { |
2b2af54a | 157 | struct dentry *dentry; |
69753a0f | 158 | struct path path; |
2b2af54a KS |
159 | int err; |
160 | ||
1ac12b4b | 161 | dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY); |
69753a0f AV |
162 | if (IS_ERR(dentry)) |
163 | return PTR_ERR(dentry); | |
164 | ||
6521f891 | 165 | err = vfs_mkdir(&init_user_ns, d_inode(path.dentry), dentry, mode); |
69753a0f AV |
166 | if (!err) |
167 | /* mark as kernel-created inode */ | |
75c3cfa8 | 168 | d_inode(dentry)->i_private = &thread; |
921a1650 | 169 | done_path_create(&path, dentry); |
2b2af54a KS |
170 | return err; |
171 | } | |
172 | ||
173 | static int create_path(const char *nodepath) | |
174 | { | |
5da4e689 AV |
175 | char *path; |
176 | char *s; | |
9d108d25 | 177 | int err = 0; |
2b2af54a | 178 | |
5da4e689 AV |
179 | /* parent directories do not exist, create them */ |
180 | path = kstrdup(nodepath, GFP_KERNEL); | |
181 | if (!path) | |
182 | return -ENOMEM; | |
183 | ||
184 | s = path; | |
185 | for (;;) { | |
186 | s = strchr(s, '/'); | |
187 | if (!s) | |
188 | break; | |
189 | s[0] = '\0'; | |
190 | err = dev_mkdir(path, 0755); | |
191 | if (err && err != -EEXIST) | |
192 | break; | |
193 | s[0] = '/'; | |
194 | s++; | |
2b2af54a | 195 | } |
5da4e689 | 196 | kfree(path); |
2b2af54a KS |
197 | return err; |
198 | } | |
199 | ||
4e4098a3 GKH |
200 | static int handle_create(const char *nodename, umode_t mode, kuid_t uid, |
201 | kgid_t gid, struct device *dev) | |
2b2af54a | 202 | { |
2b2af54a | 203 | struct dentry *dentry; |
69753a0f | 204 | struct path path; |
2b2af54a KS |
205 | int err; |
206 | ||
69753a0f AV |
207 | dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
208 | if (dentry == ERR_PTR(-ENOENT)) { | |
2b2af54a | 209 | create_path(nodename); |
69753a0f | 210 | dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
2b2af54a | 211 | } |
69753a0f AV |
212 | if (IS_ERR(dentry)) |
213 | return PTR_ERR(dentry); | |
214 | ||
6521f891 CB |
215 | err = vfs_mknod(&init_user_ns, d_inode(path.dentry), dentry, mode, |
216 | dev->devt); | |
69753a0f AV |
217 | if (!err) { |
218 | struct iattr newattrs; | |
219 | ||
69753a0f | 220 | newattrs.ia_mode = mode; |
4e4098a3 GKH |
221 | newattrs.ia_uid = uid; |
222 | newattrs.ia_gid = gid; | |
3c2670e6 | 223 | newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID; |
5955102c | 224 | inode_lock(d_inode(dentry)); |
2f221d6f | 225 | notify_change(&init_user_ns, dentry, &newattrs, NULL); |
5955102c | 226 | inode_unlock(d_inode(dentry)); |
69753a0f AV |
227 | |
228 | /* mark as kernel-created inode */ | |
75c3cfa8 | 229 | d_inode(dentry)->i_private = &thread; |
2b2af54a | 230 | } |
921a1650 | 231 | done_path_create(&path, dentry); |
2b2af54a KS |
232 | return err; |
233 | } | |
234 | ||
235 | static int dev_rmdir(const char *name) | |
236 | { | |
79714f72 | 237 | struct path parent; |
2b2af54a KS |
238 | struct dentry *dentry; |
239 | int err; | |
240 | ||
79714f72 AV |
241 | dentry = kern_path_locked(name, &parent); |
242 | if (IS_ERR(dentry)) | |
243 | return PTR_ERR(dentry); | |
75c3cfa8 DH |
244 | if (d_really_is_positive(dentry)) { |
245 | if (d_inode(dentry)->i_private == &thread) | |
6521f891 CB |
246 | err = vfs_rmdir(&init_user_ns, d_inode(parent.dentry), |
247 | dentry); | |
79714f72 AV |
248 | else |
249 | err = -EPERM; | |
2b2af54a | 250 | } else { |
79714f72 | 251 | err = -ENOENT; |
2b2af54a | 252 | } |
79714f72 | 253 | dput(dentry); |
5955102c | 254 | inode_unlock(d_inode(parent.dentry)); |
79714f72 | 255 | path_put(&parent); |
2b2af54a KS |
256 | return err; |
257 | } | |
258 | ||
259 | static int delete_path(const char *nodepath) | |
260 | { | |
be6b1dfe | 261 | char *path; |
2b2af54a KS |
262 | int err = 0; |
263 | ||
264 | path = kstrdup(nodepath, GFP_KERNEL); | |
265 | if (!path) | |
266 | return -ENOMEM; | |
267 | ||
ed413ae6 | 268 | for (;;) { |
2b2af54a KS |
269 | char *base; |
270 | ||
271 | base = strrchr(path, '/'); | |
272 | if (!base) | |
273 | break; | |
274 | base[0] = '\0'; | |
275 | err = dev_rmdir(path); | |
276 | if (err) | |
277 | break; | |
278 | } | |
279 | ||
280 | kfree(path); | |
281 | return err; | |
282 | } | |
283 | ||
284 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
285 | { | |
286 | /* did we create it */ | |
2780f1ff | 287 | if (inode->i_private != &thread) |
2b2af54a KS |
288 | return 0; |
289 | ||
290 | /* does the dev_t match */ | |
291 | if (is_blockdev(dev)) { | |
292 | if (!S_ISBLK(stat->mode)) | |
293 | return 0; | |
294 | } else { | |
295 | if (!S_ISCHR(stat->mode)) | |
296 | return 0; | |
297 | } | |
298 | if (stat->rdev != dev->devt) | |
299 | return 0; | |
300 | ||
301 | /* ours */ | |
302 | return 1; | |
303 | } | |
304 | ||
2780f1ff | 305 | static int handle_remove(const char *nodename, struct device *dev) |
2b2af54a | 306 | { |
79714f72 | 307 | struct path parent; |
2b2af54a | 308 | struct dentry *dentry; |
fbde7c61 | 309 | int deleted = 0; |
2b2af54a KS |
310 | int err; |
311 | ||
79714f72 AV |
312 | dentry = kern_path_locked(nodename, &parent); |
313 | if (IS_ERR(dentry)) | |
314 | return PTR_ERR(dentry); | |
315 | ||
75c3cfa8 | 316 | if (d_really_is_positive(dentry)) { |
79714f72 | 317 | struct kstat stat; |
3dadecce | 318 | struct path p = {.mnt = parent.mnt, .dentry = dentry}; |
a528d35e DH |
319 | err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE, |
320 | AT_STATX_SYNC_AS_STAT); | |
75c3cfa8 | 321 | if (!err && dev_mynode(dev, d_inode(dentry), &stat)) { |
79714f72 AV |
322 | struct iattr newattrs; |
323 | /* | |
324 | * before unlinking this node, reset permissions | |
325 | * of possible references like hardlinks | |
326 | */ | |
91fa2cca EB |
327 | newattrs.ia_uid = GLOBAL_ROOT_UID; |
328 | newattrs.ia_gid = GLOBAL_ROOT_GID; | |
79714f72 AV |
329 | newattrs.ia_mode = stat.mode & ~0777; |
330 | newattrs.ia_valid = | |
331 | ATTR_UID|ATTR_GID|ATTR_MODE; | |
5955102c | 332 | inode_lock(d_inode(dentry)); |
2f221d6f | 333 | notify_change(&init_user_ns, dentry, &newattrs, NULL); |
5955102c | 334 | inode_unlock(d_inode(dentry)); |
6521f891 CB |
335 | err = vfs_unlink(&init_user_ns, d_inode(parent.dentry), |
336 | dentry, NULL); | |
79714f72 AV |
337 | if (!err || err == -ENOENT) |
338 | deleted = 1; | |
2b2af54a | 339 | } |
2b2af54a | 340 | } else { |
79714f72 | 341 | err = -ENOENT; |
2b2af54a | 342 | } |
79714f72 | 343 | dput(dentry); |
5955102c | 344 | inode_unlock(d_inode(parent.dentry)); |
2b2af54a | 345 | |
79714f72 | 346 | path_put(&parent); |
2b2af54a KS |
347 | if (deleted && strchr(nodename, '/')) |
348 | delete_path(nodename); | |
2b2af54a KS |
349 | return err; |
350 | } | |
351 | ||
352 | /* | |
353 | * If configured, or requested by the commandline, devtmpfs will be | |
354 | * auto-mounted after the kernel mounted the root filesystem. | |
355 | */ | |
fad1db8a | 356 | int __init devtmpfs_mount(void) |
2b2af54a | 357 | { |
2b2af54a KS |
358 | int err; |
359 | ||
fc14f2fe | 360 | if (!mount_dev) |
2b2af54a KS |
361 | return 0; |
362 | ||
2780f1ff | 363 | if (!thread) |
2b2af54a KS |
364 | return 0; |
365 | ||
c60166f0 | 366 | err = init_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL); |
2b2af54a KS |
367 | if (err) |
368 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
369 | else | |
370 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
2b2af54a KS |
371 | return err; |
372 | } | |
373 | ||
f9e0b159 | 374 | static DECLARE_COMPLETION(setup_done); |
2780f1ff | 375 | |
4e4098a3 | 376 | static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, |
3c2670e6 | 377 | struct device *dev) |
2780f1ff AV |
378 | { |
379 | if (mode) | |
3c2670e6 | 380 | return handle_create(name, mode, uid, gid, dev); |
2780f1ff AV |
381 | else |
382 | return handle_remove(name, dev); | |
383 | } | |
384 | ||
bcbacc49 CH |
385 | static void __noreturn devtmpfs_work_loop(void) |
386 | { | |
387 | while (1) { | |
388 | spin_lock(&req_lock); | |
389 | while (requests) { | |
390 | struct req *req = requests; | |
391 | requests = NULL; | |
392 | spin_unlock(&req_lock); | |
393 | while (req) { | |
394 | struct req *next = req->next; | |
395 | req->err = handle(req->name, req->mode, | |
396 | req->uid, req->gid, req->dev); | |
397 | complete(&req->done); | |
398 | req = next; | |
399 | } | |
400 | spin_lock(&req_lock); | |
401 | } | |
402 | __set_current_state(TASK_INTERRUPTIBLE); | |
403 | spin_unlock(&req_lock); | |
404 | schedule(); | |
405 | } | |
406 | } | |
407 | ||
408 | static int __init devtmpfs_setup(void *p) | |
2780f1ff | 409 | { |
c9d6b287 RV |
410 | int err; |
411 | ||
412 | err = ksys_unshare(CLONE_NEWNS); | |
413 | if (err) | |
2780f1ff | 414 | goto out; |
c60166f0 | 415 | err = init_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL); |
c9d6b287 | 416 | if (err) |
2780f1ff | 417 | goto out; |
db63f1e3 | 418 | init_chdir("/.."); /* will traverse into overmounted root */ |
4b7ca501 | 419 | init_chroot("."); |
0ff0e95e RV |
420 | out: |
421 | *(int *)p = err; | |
2780f1ff | 422 | complete(&setup_done); |
0ff0e95e RV |
423 | return err; |
424 | } | |
425 | ||
bcbacc49 CH |
426 | /* |
427 | * The __ref is because devtmpfs_setup needs to be __init for the routines it | |
428 | * calls. That call is done while devtmpfs_init, which is marked __init, | |
429 | * synchronously waits for it to complete. | |
430 | */ | |
431 | static int __ref devtmpfsd(void *p) | |
0ff0e95e RV |
432 | { |
433 | int err = devtmpfs_setup(p); | |
434 | ||
435 | if (err) | |
436 | return err; | |
bcbacc49 | 437 | devtmpfs_work_loop(); |
2780f1ff | 438 | return 0; |
2780f1ff AV |
439 | } |
440 | ||
2b2af54a KS |
441 | /* |
442 | * Create devtmpfs instance, driver-core devices will add their device | |
443 | * nodes here. | |
444 | */ | |
445 | int __init devtmpfs_init(void) | |
446 | { | |
d401727e AV |
447 | char opts[] = "mode=0755"; |
448 | int err; | |
449 | ||
450 | mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts); | |
451 | if (IS_ERR(mnt)) { | |
452 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %ld\n", | |
453 | PTR_ERR(mnt)); | |
454 | return PTR_ERR(mnt); | |
455 | } | |
456 | err = register_filesystem(&dev_fs_type); | |
2b2af54a KS |
457 | if (err) { |
458 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
459 | "type %i\n", err); | |
460 | return err; | |
461 | } | |
462 | ||
2780f1ff AV |
463 | thread = kthread_run(devtmpfsd, &err, "kdevtmpfs"); |
464 | if (!IS_ERR(thread)) { | |
465 | wait_for_completion(&setup_done); | |
466 | } else { | |
467 | err = PTR_ERR(thread); | |
468 | thread = NULL; | |
469 | } | |
470 | ||
471 | if (err) { | |
2b2af54a KS |
472 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); |
473 | unregister_filesystem(&dev_fs_type); | |
474 | return err; | |
475 | } | |
2b2af54a KS |
476 | |
477 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
478 | return 0; | |
479 | } |