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> |
e262e32d | 28 | #include <uapi/linux/mount.h> |
c3a30420 | 29 | #include "base.h" |
2b2af54a | 30 | |
2780f1ff | 31 | static struct task_struct *thread; |
2b2af54a KS |
32 | |
33 | #if defined CONFIG_DEVTMPFS_MOUNT | |
fc14f2fe | 34 | static int mount_dev = 1; |
2b2af54a | 35 | #else |
fc14f2fe | 36 | static int mount_dev; |
2b2af54a KS |
37 | #endif |
38 | ||
2780f1ff AV |
39 | static DEFINE_SPINLOCK(req_lock); |
40 | ||
41 | static struct req { | |
42 | struct req *next; | |
43 | struct completion done; | |
44 | int err; | |
45 | const char *name; | |
2c9ede55 | 46 | umode_t mode; /* 0 => delete */ |
4e4098a3 GKH |
47 | kuid_t uid; |
48 | kgid_t gid; | |
2780f1ff AV |
49 | struct device *dev; |
50 | } *requests; | |
ed413ae6 | 51 | |
2b2af54a KS |
52 | static int __init mount_param(char *str) |
53 | { | |
fc14f2fe | 54 | mount_dev = simple_strtoul(str, NULL, 0); |
2b2af54a KS |
55 | return 1; |
56 | } | |
57 | __setup("devtmpfs.mount=", mount_param); | |
58 | ||
fc14f2fe AV |
59 | static struct dentry *dev_mount(struct file_system_type *fs_type, int flags, |
60 | const char *dev_name, void *data) | |
2b2af54a | 61 | { |
da5e4ef7 | 62 | #ifdef CONFIG_TMPFS |
fc14f2fe | 63 | return mount_single(fs_type, flags, data, shmem_fill_super); |
da5e4ef7 | 64 | #else |
fc14f2fe | 65 | return mount_single(fs_type, flags, data, ramfs_fill_super); |
da5e4ef7 | 66 | #endif |
2b2af54a KS |
67 | } |
68 | ||
69 | static struct file_system_type dev_fs_type = { | |
70 | .name = "devtmpfs", | |
fc14f2fe | 71 | .mount = dev_mount, |
2b2af54a KS |
72 | .kill_sb = kill_litter_super, |
73 | }; | |
74 | ||
75 | #ifdef CONFIG_BLOCK | |
76 | static inline int is_blockdev(struct device *dev) | |
77 | { | |
78 | return dev->class == &block_class; | |
79 | } | |
80 | #else | |
81 | static inline int is_blockdev(struct device *dev) { return 0; } | |
82 | #endif | |
83 | ||
2780f1ff AV |
84 | int devtmpfs_create_node(struct device *dev) |
85 | { | |
86 | const char *tmp = NULL; | |
87 | struct req req; | |
88 | ||
89 | if (!thread) | |
90 | return 0; | |
91 | ||
92 | req.mode = 0; | |
4e4098a3 GKH |
93 | req.uid = GLOBAL_ROOT_UID; |
94 | req.gid = GLOBAL_ROOT_GID; | |
3c2670e6 | 95 | req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp); |
2780f1ff AV |
96 | if (!req.name) |
97 | return -ENOMEM; | |
98 | ||
99 | if (req.mode == 0) | |
100 | req.mode = 0600; | |
101 | if (is_blockdev(dev)) | |
102 | req.mode |= S_IFBLK; | |
103 | else | |
104 | req.mode |= S_IFCHR; | |
105 | ||
106 | req.dev = dev; | |
107 | ||
108 | init_completion(&req.done); | |
109 | ||
110 | spin_lock(&req_lock); | |
111 | req.next = requests; | |
112 | requests = &req; | |
113 | spin_unlock(&req_lock); | |
114 | ||
115 | wake_up_process(thread); | |
116 | wait_for_completion(&req.done); | |
117 | ||
118 | kfree(tmp); | |
119 | ||
120 | return req.err; | |
121 | } | |
122 | ||
123 | int devtmpfs_delete_node(struct device *dev) | |
124 | { | |
125 | const char *tmp = NULL; | |
126 | struct req req; | |
127 | ||
128 | if (!thread) | |
129 | return 0; | |
130 | ||
3c2670e6 | 131 | req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp); |
2780f1ff AV |
132 | if (!req.name) |
133 | return -ENOMEM; | |
134 | ||
135 | req.mode = 0; | |
136 | req.dev = dev; | |
137 | ||
138 | init_completion(&req.done); | |
139 | ||
140 | spin_lock(&req_lock); | |
141 | req.next = requests; | |
142 | requests = &req; | |
143 | spin_unlock(&req_lock); | |
144 | ||
145 | wake_up_process(thread); | |
146 | wait_for_completion(&req.done); | |
147 | ||
148 | kfree(tmp); | |
149 | return req.err; | |
150 | } | |
151 | ||
fbd48a69 | 152 | static int dev_mkdir(const char *name, umode_t mode) |
2b2af54a | 153 | { |
2b2af54a | 154 | struct dentry *dentry; |
69753a0f | 155 | struct path path; |
2b2af54a KS |
156 | int err; |
157 | ||
1ac12b4b | 158 | dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY); |
69753a0f AV |
159 | if (IS_ERR(dentry)) |
160 | return PTR_ERR(dentry); | |
161 | ||
75c3cfa8 | 162 | err = vfs_mkdir(d_inode(path.dentry), dentry, mode); |
69753a0f AV |
163 | if (!err) |
164 | /* mark as kernel-created inode */ | |
75c3cfa8 | 165 | d_inode(dentry)->i_private = &thread; |
921a1650 | 166 | done_path_create(&path, dentry); |
2b2af54a KS |
167 | return err; |
168 | } | |
169 | ||
170 | static int create_path(const char *nodepath) | |
171 | { | |
5da4e689 AV |
172 | char *path; |
173 | char *s; | |
9d108d25 | 174 | int err = 0; |
2b2af54a | 175 | |
5da4e689 AV |
176 | /* parent directories do not exist, create them */ |
177 | path = kstrdup(nodepath, GFP_KERNEL); | |
178 | if (!path) | |
179 | return -ENOMEM; | |
180 | ||
181 | s = path; | |
182 | for (;;) { | |
183 | s = strchr(s, '/'); | |
184 | if (!s) | |
185 | break; | |
186 | s[0] = '\0'; | |
187 | err = dev_mkdir(path, 0755); | |
188 | if (err && err != -EEXIST) | |
189 | break; | |
190 | s[0] = '/'; | |
191 | s++; | |
2b2af54a | 192 | } |
5da4e689 | 193 | kfree(path); |
2b2af54a KS |
194 | return err; |
195 | } | |
196 | ||
4e4098a3 GKH |
197 | static int handle_create(const char *nodename, umode_t mode, kuid_t uid, |
198 | kgid_t gid, struct device *dev) | |
2b2af54a | 199 | { |
2b2af54a | 200 | struct dentry *dentry; |
69753a0f | 201 | struct path path; |
2b2af54a KS |
202 | int err; |
203 | ||
69753a0f AV |
204 | dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
205 | if (dentry == ERR_PTR(-ENOENT)) { | |
2b2af54a | 206 | create_path(nodename); |
69753a0f | 207 | dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
2b2af54a | 208 | } |
69753a0f AV |
209 | if (IS_ERR(dentry)) |
210 | return PTR_ERR(dentry); | |
211 | ||
75c3cfa8 | 212 | err = vfs_mknod(d_inode(path.dentry), dentry, mode, dev->devt); |
69753a0f AV |
213 | if (!err) { |
214 | struct iattr newattrs; | |
215 | ||
69753a0f | 216 | newattrs.ia_mode = mode; |
4e4098a3 GKH |
217 | newattrs.ia_uid = uid; |
218 | newattrs.ia_gid = gid; | |
3c2670e6 | 219 | newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID; |
5955102c | 220 | inode_lock(d_inode(dentry)); |
27ac0ffe | 221 | notify_change(dentry, &newattrs, NULL); |
5955102c | 222 | inode_unlock(d_inode(dentry)); |
69753a0f AV |
223 | |
224 | /* mark as kernel-created inode */ | |
75c3cfa8 | 225 | d_inode(dentry)->i_private = &thread; |
2b2af54a | 226 | } |
921a1650 | 227 | done_path_create(&path, dentry); |
2b2af54a KS |
228 | return err; |
229 | } | |
230 | ||
231 | static int dev_rmdir(const char *name) | |
232 | { | |
79714f72 | 233 | struct path parent; |
2b2af54a KS |
234 | struct dentry *dentry; |
235 | int err; | |
236 | ||
79714f72 AV |
237 | dentry = kern_path_locked(name, &parent); |
238 | if (IS_ERR(dentry)) | |
239 | return PTR_ERR(dentry); | |
75c3cfa8 DH |
240 | if (d_really_is_positive(dentry)) { |
241 | if (d_inode(dentry)->i_private == &thread) | |
242 | err = vfs_rmdir(d_inode(parent.dentry), dentry); | |
79714f72 AV |
243 | else |
244 | err = -EPERM; | |
2b2af54a | 245 | } else { |
79714f72 | 246 | err = -ENOENT; |
2b2af54a | 247 | } |
79714f72 | 248 | dput(dentry); |
5955102c | 249 | inode_unlock(d_inode(parent.dentry)); |
79714f72 | 250 | path_put(&parent); |
2b2af54a KS |
251 | return err; |
252 | } | |
253 | ||
254 | static int delete_path(const char *nodepath) | |
255 | { | |
be6b1dfe | 256 | char *path; |
2b2af54a KS |
257 | int err = 0; |
258 | ||
259 | path = kstrdup(nodepath, GFP_KERNEL); | |
260 | if (!path) | |
261 | return -ENOMEM; | |
262 | ||
ed413ae6 | 263 | for (;;) { |
2b2af54a KS |
264 | char *base; |
265 | ||
266 | base = strrchr(path, '/'); | |
267 | if (!base) | |
268 | break; | |
269 | base[0] = '\0'; | |
270 | err = dev_rmdir(path); | |
271 | if (err) | |
272 | break; | |
273 | } | |
274 | ||
275 | kfree(path); | |
276 | return err; | |
277 | } | |
278 | ||
279 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
280 | { | |
281 | /* did we create it */ | |
2780f1ff | 282 | if (inode->i_private != &thread) |
2b2af54a KS |
283 | return 0; |
284 | ||
285 | /* does the dev_t match */ | |
286 | if (is_blockdev(dev)) { | |
287 | if (!S_ISBLK(stat->mode)) | |
288 | return 0; | |
289 | } else { | |
290 | if (!S_ISCHR(stat->mode)) | |
291 | return 0; | |
292 | } | |
293 | if (stat->rdev != dev->devt) | |
294 | return 0; | |
295 | ||
296 | /* ours */ | |
297 | return 1; | |
298 | } | |
299 | ||
2780f1ff | 300 | static int handle_remove(const char *nodename, struct device *dev) |
2b2af54a | 301 | { |
79714f72 | 302 | struct path parent; |
2b2af54a | 303 | struct dentry *dentry; |
fbde7c61 | 304 | int deleted = 0; |
2b2af54a KS |
305 | int err; |
306 | ||
79714f72 AV |
307 | dentry = kern_path_locked(nodename, &parent); |
308 | if (IS_ERR(dentry)) | |
309 | return PTR_ERR(dentry); | |
310 | ||
75c3cfa8 | 311 | if (d_really_is_positive(dentry)) { |
79714f72 | 312 | struct kstat stat; |
3dadecce | 313 | struct path p = {.mnt = parent.mnt, .dentry = dentry}; |
a528d35e DH |
314 | err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE, |
315 | AT_STATX_SYNC_AS_STAT); | |
75c3cfa8 | 316 | if (!err && dev_mynode(dev, d_inode(dentry), &stat)) { |
79714f72 AV |
317 | struct iattr newattrs; |
318 | /* | |
319 | * before unlinking this node, reset permissions | |
320 | * of possible references like hardlinks | |
321 | */ | |
91fa2cca EB |
322 | newattrs.ia_uid = GLOBAL_ROOT_UID; |
323 | newattrs.ia_gid = GLOBAL_ROOT_GID; | |
79714f72 AV |
324 | newattrs.ia_mode = stat.mode & ~0777; |
325 | newattrs.ia_valid = | |
326 | ATTR_UID|ATTR_GID|ATTR_MODE; | |
5955102c | 327 | inode_lock(d_inode(dentry)); |
27ac0ffe | 328 | notify_change(dentry, &newattrs, NULL); |
5955102c | 329 | inode_unlock(d_inode(dentry)); |
75c3cfa8 | 330 | err = vfs_unlink(d_inode(parent.dentry), dentry, NULL); |
79714f72 AV |
331 | if (!err || err == -ENOENT) |
332 | deleted = 1; | |
2b2af54a | 333 | } |
2b2af54a | 334 | } else { |
79714f72 | 335 | err = -ENOENT; |
2b2af54a | 336 | } |
79714f72 | 337 | dput(dentry); |
5955102c | 338 | inode_unlock(d_inode(parent.dentry)); |
2b2af54a | 339 | |
79714f72 | 340 | path_put(&parent); |
2b2af54a KS |
341 | if (deleted && strchr(nodename, '/')) |
342 | delete_path(nodename); | |
2b2af54a KS |
343 | return err; |
344 | } | |
345 | ||
346 | /* | |
347 | * If configured, or requested by the commandline, devtmpfs will be | |
348 | * auto-mounted after the kernel mounted the root filesystem. | |
349 | */ | |
073120cc | 350 | int devtmpfs_mount(const char *mntdir) |
2b2af54a | 351 | { |
2b2af54a KS |
352 | int err; |
353 | ||
fc14f2fe | 354 | if (!mount_dev) |
2b2af54a KS |
355 | return 0; |
356 | ||
2780f1ff | 357 | if (!thread) |
2b2af54a KS |
358 | return 0; |
359 | ||
312db1aa DB |
360 | err = ksys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, |
361 | NULL); | |
2b2af54a KS |
362 | if (err) |
363 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
364 | else | |
365 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
2b2af54a KS |
366 | return err; |
367 | } | |
368 | ||
f9e0b159 | 369 | static DECLARE_COMPLETION(setup_done); |
2780f1ff | 370 | |
4e4098a3 | 371 | static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, |
3c2670e6 | 372 | struct device *dev) |
2780f1ff AV |
373 | { |
374 | if (mode) | |
3c2670e6 | 375 | return handle_create(name, mode, uid, gid, dev); |
2780f1ff AV |
376 | else |
377 | return handle_remove(name, dev); | |
378 | } | |
379 | ||
380 | static int devtmpfsd(void *p) | |
381 | { | |
382 | char options[] = "mode=0755"; | |
383 | int *err = p; | |
9b32105e | 384 | *err = ksys_unshare(CLONE_NEWNS); |
2780f1ff AV |
385 | if (*err) |
386 | goto out; | |
312db1aa | 387 | *err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options); |
2780f1ff AV |
388 | if (*err) |
389 | goto out; | |
447016e9 | 390 | ksys_chdir("/.."); /* will traverse into overmounted root */ |
a16fe33a | 391 | ksys_chroot("."); |
2780f1ff AV |
392 | complete(&setup_done); |
393 | while (1) { | |
394 | spin_lock(&req_lock); | |
395 | while (requests) { | |
396 | struct req *req = requests; | |
397 | requests = NULL; | |
398 | spin_unlock(&req_lock); | |
399 | while (req) { | |
e13889ba | 400 | struct req *next = req->next; |
3c2670e6 KS |
401 | req->err = handle(req->name, req->mode, |
402 | req->uid, req->gid, req->dev); | |
2780f1ff | 403 | complete(&req->done); |
e13889ba | 404 | req = next; |
2780f1ff AV |
405 | } |
406 | spin_lock(&req_lock); | |
407 | } | |
65e6757b | 408 | __set_current_state(TASK_INTERRUPTIBLE); |
2780f1ff AV |
409 | spin_unlock(&req_lock); |
410 | schedule(); | |
2780f1ff AV |
411 | } |
412 | return 0; | |
413 | out: | |
414 | complete(&setup_done); | |
415 | return *err; | |
416 | } | |
417 | ||
2b2af54a KS |
418 | /* |
419 | * Create devtmpfs instance, driver-core devices will add their device | |
420 | * nodes here. | |
421 | */ | |
422 | int __init devtmpfs_init(void) | |
423 | { | |
2780f1ff | 424 | int err = register_filesystem(&dev_fs_type); |
2b2af54a KS |
425 | if (err) { |
426 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
427 | "type %i\n", err); | |
428 | return err; | |
429 | } | |
430 | ||
2780f1ff AV |
431 | thread = kthread_run(devtmpfsd, &err, "kdevtmpfs"); |
432 | if (!IS_ERR(thread)) { | |
433 | wait_for_completion(&setup_done); | |
434 | } else { | |
435 | err = PTR_ERR(thread); | |
436 | thread = NULL; | |
437 | } | |
438 | ||
439 | if (err) { | |
2b2af54a KS |
440 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); |
441 | unregister_filesystem(&dev_fs_type); | |
442 | return err; | |
443 | } | |
2b2af54a KS |
444 | |
445 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
446 | return 0; | |
447 | } |