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3e0a4e85 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
1da177e4 LT |
2 | /* |
3 | * Directory notifications for Linux. | |
4 | * | |
5 | * Copyright (C) 2000,2001,2002 Stephen Rothwell | |
6 | * | |
3c5119c0 EP |
7 | * Copyright (C) 2009 Eric Paris <Red Hat Inc> |
8 | * dnotify was largly rewritten to use the new fsnotify infrastructure | |
1da177e4 LT |
9 | */ |
10 | #include <linux/fs.h> | |
11 | #include <linux/module.h> | |
12 | #include <linux/sched.h> | |
01919134 | 13 | #include <linux/sched/signal.h> |
1da177e4 LT |
14 | #include <linux/dnotify.h> |
15 | #include <linux/init.h> | |
16 | #include <linux/spinlock.h> | |
17 | #include <linux/slab.h> | |
9f3acc31 | 18 | #include <linux/fdtable.h> |
3c5119c0 | 19 | #include <linux/fsnotify_backend.h> |
1da177e4 | 20 | |
fa3536cc | 21 | int dir_notify_enable __read_mostly = 1; |
1da177e4 | 22 | |
3c5119c0 | 23 | static struct kmem_cache *dnotify_struct_cache __read_mostly; |
ef5e2b78 | 24 | static struct kmem_cache *dnotify_mark_cache __read_mostly; |
3c5119c0 | 25 | static struct fsnotify_group *dnotify_group __read_mostly; |
3c5119c0 EP |
26 | |
27 | /* | |
e61ce867 | 28 | * dnotify will attach one of these to each inode (i_fsnotify_marks) which |
3c5119c0 EP |
29 | * is being watched by dnotify. If multiple userspace applications are watching |
30 | * the same directory with dnotify their information is chained in dn | |
31 | */ | |
ef5e2b78 EP |
32 | struct dnotify_mark { |
33 | struct fsnotify_mark fsn_mark; | |
3c5119c0 EP |
34 | struct dnotify_struct *dn; |
35 | }; | |
1da177e4 | 36 | |
3c5119c0 EP |
37 | /* |
38 | * When a process starts or stops watching an inode the set of events which | |
39 | * dnotify cares about for that inode may change. This function runs the | |
40 | * list of everything receiving dnotify events about this directory and calculates | |
41 | * the set of all those events. After it updates what dnotify is interested in | |
42 | * it calls the fsnotify function so it can update the set of all events relevant | |
43 | * to this inode. | |
44 | */ | |
ef5e2b78 | 45 | static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark) |
1da177e4 | 46 | { |
66d2b81b | 47 | __u32 new_mask = 0; |
1da177e4 | 48 | struct dnotify_struct *dn; |
ef5e2b78 EP |
49 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
50 | struct dnotify_mark, | |
51 | fsn_mark); | |
3c5119c0 | 52 | |
ef5e2b78 | 53 | assert_spin_locked(&fsn_mark->lock); |
1da177e4 | 54 | |
ef5e2b78 | 55 | for (dn = dn_mark->dn; dn != NULL; dn = dn->dn_next) |
3c5119c0 | 56 | new_mask |= (dn->dn_mask & ~FS_DN_MULTISHOT); |
66d2b81b | 57 | if (fsn_mark->mask == new_mask) |
3c5119c0 | 58 | return; |
66d2b81b | 59 | fsn_mark->mask = new_mask; |
3c5119c0 | 60 | |
a242677b | 61 | fsnotify_recalc_mask(fsn_mark->connector); |
1da177e4 LT |
62 | } |
63 | ||
3c5119c0 EP |
64 | /* |
65 | * Mains fsnotify call where events are delivered to dnotify. | |
66 | * Find the dnotify mark on the relevant inode, run the list of dnotify structs | |
67 | * on that mark and determine which of them has expressed interest in receiving | |
68 | * events of this type. When found send the correct process and signal and | |
69 | * destroy the dnotify struct if it was not registered to receive multiple | |
70 | * events. | |
71 | */ | |
72 | static int dnotify_handle_event(struct fsnotify_group *group, | |
7053aee2 | 73 | struct inode *inode, |
3cd5eca8 | 74 | u32 mask, const void *data, int data_type, |
e43e9c33 | 75 | const struct qstr *file_name, u32 cookie, |
9385a84d | 76 | struct fsnotify_iter_info *iter_info) |
3c5119c0 | 77 | { |
5b0457ad | 78 | struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info); |
ef5e2b78 | 79 | struct dnotify_mark *dn_mark; |
3c5119c0 EP |
80 | struct dnotify_struct *dn; |
81 | struct dnotify_struct **prev; | |
82 | struct fown_struct *fown; | |
7053aee2 | 83 | __u32 test_mask = mask & ~FS_EVENT_ON_CHILD; |
3c5119c0 | 84 | |
83c4c4b0 JK |
85 | /* not a dir, dnotify doesn't care */ |
86 | if (!S_ISDIR(inode->i_mode)) | |
87 | return 0; | |
88 | ||
5b0457ad AG |
89 | if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info))) |
90 | return 0; | |
ce8f76fb | 91 | |
ce8f76fb | 92 | dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 | 93 | |
ce8f76fb | 94 | spin_lock(&inode_mark->lock); |
ef5e2b78 | 95 | prev = &dn_mark->dn; |
3c5119c0 | 96 | while ((dn = *prev) != NULL) { |
94552684 | 97 | if ((dn->dn_mask & test_mask) == 0) { |
3c5119c0 EP |
98 | prev = &dn->dn_next; |
99 | continue; | |
100 | } | |
101 | fown = &dn->dn_filp->f_owner; | |
102 | send_sigio(fown, dn->dn_fd, POLL_MSG); | |
103 | if (dn->dn_mask & FS_DN_MULTISHOT) | |
104 | prev = &dn->dn_next; | |
105 | else { | |
106 | *prev = dn->dn_next; | |
107 | kmem_cache_free(dnotify_struct_cache, dn); | |
ce8f76fb | 108 | dnotify_recalc_inode_mask(inode_mark); |
3c5119c0 EP |
109 | } |
110 | } | |
111 | ||
ce8f76fb | 112 | spin_unlock(&inode_mark->lock); |
3c5119c0 EP |
113 | |
114 | return 0; | |
115 | } | |
116 | ||
ef5e2b78 | 117 | static void dnotify_free_mark(struct fsnotify_mark *fsn_mark) |
3c5119c0 | 118 | { |
ef5e2b78 EP |
119 | struct dnotify_mark *dn_mark = container_of(fsn_mark, |
120 | struct dnotify_mark, | |
121 | fsn_mark); | |
3c5119c0 | 122 | |
ef5e2b78 | 123 | BUG_ON(dn_mark->dn); |
3c5119c0 | 124 | |
ef5e2b78 | 125 | kmem_cache_free(dnotify_mark_cache, dn_mark); |
3c5119c0 EP |
126 | } |
127 | ||
c9ea9df3 | 128 | static const struct fsnotify_ops dnotify_fsnotify_ops = { |
3c5119c0 | 129 | .handle_event = dnotify_handle_event, |
054c636e | 130 | .free_mark = dnotify_free_mark, |
3c5119c0 EP |
131 | }; |
132 | ||
133 | /* | |
134 | * Called every time a file is closed. Looks first for a dnotify mark on the | |
e61ce867 | 135 | * inode. If one is found run all of the ->dn structures attached to that |
3c5119c0 EP |
136 | * mark for one relevant to this process closing the file and remove that |
137 | * dnotify_struct. If that was the last dnotify_struct also remove the | |
e61ce867 | 138 | * fsnotify_mark. |
3c5119c0 | 139 | */ |
1da177e4 LT |
140 | void dnotify_flush(struct file *filp, fl_owner_t id) |
141 | { | |
ef5e2b78 EP |
142 | struct fsnotify_mark *fsn_mark; |
143 | struct dnotify_mark *dn_mark; | |
1da177e4 LT |
144 | struct dnotify_struct *dn; |
145 | struct dnotify_struct **prev; | |
146 | struct inode *inode; | |
4712e722 | 147 | bool free = false; |
1da177e4 | 148 | |
496ad9aa | 149 | inode = file_inode(filp); |
1da177e4 LT |
150 | if (!S_ISDIR(inode->i_mode)) |
151 | return; | |
3c5119c0 | 152 | |
b1362edf | 153 | fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group); |
ef5e2b78 | 154 | if (!fsn_mark) |
3c5119c0 | 155 | return; |
ef5e2b78 | 156 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); |
3c5119c0 | 157 | |
52f85729 | 158 | mutex_lock(&dnotify_group->mark_mutex); |
3c5119c0 | 159 | |
ef5e2b78 EP |
160 | spin_lock(&fsn_mark->lock); |
161 | prev = &dn_mark->dn; | |
1da177e4 LT |
162 | while ((dn = *prev) != NULL) { |
163 | if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { | |
164 | *prev = dn->dn_next; | |
3c5119c0 | 165 | kmem_cache_free(dnotify_struct_cache, dn); |
ef5e2b78 | 166 | dnotify_recalc_inode_mask(fsn_mark); |
1da177e4 LT |
167 | break; |
168 | } | |
169 | prev = &dn->dn_next; | |
170 | } | |
3c5119c0 | 171 | |
ef5e2b78 | 172 | spin_unlock(&fsn_mark->lock); |
3c5119c0 | 173 | |
52f85729 LS |
174 | /* nothing else could have found us thanks to the dnotify_groups |
175 | mark_mutex */ | |
4712e722 JK |
176 | if (dn_mark->dn == NULL) { |
177 | fsnotify_detach_mark(fsn_mark); | |
178 | free = true; | |
179 | } | |
3c5119c0 | 180 | |
52f85729 | 181 | mutex_unlock(&dnotify_group->mark_mutex); |
3c5119c0 | 182 | |
4712e722 JK |
183 | if (free) |
184 | fsnotify_free_mark(fsn_mark); | |
ef5e2b78 | 185 | fsnotify_put_mark(fsn_mark); |
3c5119c0 EP |
186 | } |
187 | ||
188 | /* this conversion is done only at watch creation */ | |
189 | static __u32 convert_arg(unsigned long arg) | |
190 | { | |
191 | __u32 new_mask = FS_EVENT_ON_CHILD; | |
192 | ||
193 | if (arg & DN_MULTISHOT) | |
194 | new_mask |= FS_DN_MULTISHOT; | |
195 | if (arg & DN_DELETE) | |
196 | new_mask |= (FS_DELETE | FS_MOVED_FROM); | |
197 | if (arg & DN_MODIFY) | |
198 | new_mask |= FS_MODIFY; | |
199 | if (arg & DN_ACCESS) | |
200 | new_mask |= FS_ACCESS; | |
201 | if (arg & DN_ATTRIB) | |
202 | new_mask |= FS_ATTRIB; | |
203 | if (arg & DN_RENAME) | |
204 | new_mask |= FS_DN_RENAME; | |
205 | if (arg & DN_CREATE) | |
206 | new_mask |= (FS_CREATE | FS_MOVED_TO); | |
207 | ||
208 | return new_mask; | |
1da177e4 LT |
209 | } |
210 | ||
3c5119c0 EP |
211 | /* |
212 | * If multiple processes watch the same inode with dnotify there is only one | |
e61ce867 | 213 | * dnotify mark in inode->i_fsnotify_marks but we chain a dnotify_struct |
3c5119c0 EP |
214 | * onto that mark. This function either attaches the new dnotify_struct onto |
215 | * that list, or it |= the mask onto an existing dnofiy_struct. | |
216 | */ | |
ef5e2b78 | 217 | static int attach_dn(struct dnotify_struct *dn, struct dnotify_mark *dn_mark, |
3c5119c0 EP |
218 | fl_owner_t id, int fd, struct file *filp, __u32 mask) |
219 | { | |
220 | struct dnotify_struct *odn; | |
221 | ||
ef5e2b78 | 222 | odn = dn_mark->dn; |
3c5119c0 EP |
223 | while (odn != NULL) { |
224 | /* adding more events to existing dnofiy_struct? */ | |
225 | if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { | |
226 | odn->dn_fd = fd; | |
227 | odn->dn_mask |= mask; | |
228 | return -EEXIST; | |
229 | } | |
230 | odn = odn->dn_next; | |
231 | } | |
232 | ||
233 | dn->dn_mask = mask; | |
234 | dn->dn_fd = fd; | |
235 | dn->dn_filp = filp; | |
236 | dn->dn_owner = id; | |
ef5e2b78 EP |
237 | dn->dn_next = dn_mark->dn; |
238 | dn_mark->dn = dn; | |
3c5119c0 EP |
239 | |
240 | return 0; | |
241 | } | |
242 | ||
243 | /* | |
244 | * When a process calls fcntl to attach a dnotify watch to a directory it ends | |
245 | * up here. Allocate both a mark for fsnotify to add and a dnotify_struct to be | |
246 | * attached to the fsnotify_mark. | |
247 | */ | |
1da177e4 LT |
248 | int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) |
249 | { | |
ef5e2b78 EP |
250 | struct dnotify_mark *new_dn_mark, *dn_mark; |
251 | struct fsnotify_mark *new_fsn_mark, *fsn_mark; | |
1da177e4 | 252 | struct dnotify_struct *dn; |
1da177e4 LT |
253 | struct inode *inode; |
254 | fl_owner_t id = current->files; | |
214b7049 | 255 | struct file *f; |
3c5119c0 EP |
256 | int destroy = 0, error = 0; |
257 | __u32 mask; | |
258 | ||
259 | /* we use these to tell if we need to kfree */ | |
ef5e2b78 | 260 | new_fsn_mark = NULL; |
3c5119c0 | 261 | dn = NULL; |
1da177e4 | 262 | |
3c5119c0 EP |
263 | if (!dir_notify_enable) { |
264 | error = -EINVAL; | |
265 | goto out_err; | |
266 | } | |
267 | ||
268 | /* a 0 mask means we are explicitly removing the watch */ | |
1da177e4 LT |
269 | if ((arg & ~DN_MULTISHOT) == 0) { |
270 | dnotify_flush(filp, id); | |
3c5119c0 EP |
271 | error = 0; |
272 | goto out_err; | |
1da177e4 | 273 | } |
3c5119c0 EP |
274 | |
275 | /* dnotify only works on directories */ | |
496ad9aa | 276 | inode = file_inode(filp); |
3c5119c0 EP |
277 | if (!S_ISDIR(inode->i_mode)) { |
278 | error = -ENOTDIR; | |
279 | goto out_err; | |
1da177e4 LT |
280 | } |
281 | ||
3c5119c0 EP |
282 | /* expect most fcntl to add new rather than augment old */ |
283 | dn = kmem_cache_alloc(dnotify_struct_cache, GFP_KERNEL); | |
284 | if (!dn) { | |
285 | error = -ENOMEM; | |
286 | goto out_err; | |
287 | } | |
214b7049 | 288 | |
3c5119c0 | 289 | /* new fsnotify mark, we expect most fcntl calls to add a new mark */ |
ef5e2b78 EP |
290 | new_dn_mark = kmem_cache_alloc(dnotify_mark_cache, GFP_KERNEL); |
291 | if (!new_dn_mark) { | |
3c5119c0 EP |
292 | error = -ENOMEM; |
293 | goto out_err; | |
294 | } | |
1da177e4 | 295 | |
3c5119c0 EP |
296 | /* convert the userspace DN_* "arg" to the internal FS_* defines in fsnotify */ |
297 | mask = convert_arg(arg); | |
1da177e4 | 298 | |
ef5e2b78 EP |
299 | /* set up the new_fsn_mark and new_dn_mark */ |
300 | new_fsn_mark = &new_dn_mark->fsn_mark; | |
054c636e | 301 | fsnotify_init_mark(new_fsn_mark, dnotify_group); |
ef5e2b78 EP |
302 | new_fsn_mark->mask = mask; |
303 | new_dn_mark->dn = NULL; | |
1da177e4 | 304 | |
3c5119c0 | 305 | /* this is needed to prevent the fcntl/close race described below */ |
52f85729 | 306 | mutex_lock(&dnotify_group->mark_mutex); |
1da177e4 | 307 | |
ef5e2b78 | 308 | /* add the new_fsn_mark or find an old one. */ |
b1362edf | 309 | fsn_mark = fsnotify_find_mark(&inode->i_fsnotify_marks, dnotify_group); |
ef5e2b78 EP |
310 | if (fsn_mark) { |
311 | dn_mark = container_of(fsn_mark, struct dnotify_mark, fsn_mark); | |
312 | spin_lock(&fsn_mark->lock); | |
3c5119c0 | 313 | } else { |
b249f5be | 314 | error = fsnotify_add_inode_mark_locked(new_fsn_mark, inode, 0); |
b3a00660 JK |
315 | if (error) { |
316 | mutex_unlock(&dnotify_group->mark_mutex); | |
317 | goto out_err; | |
318 | } | |
ef5e2b78 EP |
319 | spin_lock(&new_fsn_mark->lock); |
320 | fsn_mark = new_fsn_mark; | |
321 | dn_mark = new_dn_mark; | |
322 | /* we used new_fsn_mark, so don't free it */ | |
323 | new_fsn_mark = NULL; | |
3c5119c0 | 324 | } |
1da177e4 | 325 | |
3c5119c0 EP |
326 | rcu_read_lock(); |
327 | f = fcheck(fd); | |
328 | rcu_read_unlock(); | |
1da177e4 | 329 | |
3c5119c0 EP |
330 | /* if (f != filp) means that we lost a race and another task/thread |
331 | * actually closed the fd we are still playing with before we grabbed | |
52f85729 LS |
332 | * the dnotify_groups mark_mutex and fsn_mark->lock. Since closing the |
333 | * fd is the only time we clean up the marks we need to get our mark | |
334 | * off the list. */ | |
3c5119c0 EP |
335 | if (f != filp) { |
336 | /* if we added ourselves, shoot ourselves, it's possible that | |
ef5e2b78 | 337 | * the flush actually did shoot this fsn_mark. That's fine too |
3c5119c0 | 338 | * since multiple calls to destroy_mark is perfectly safe, if |
ef5e2b78 | 339 | * we found a dn_mark already attached to the inode, just sod |
3c5119c0 EP |
340 | * off silently as the flush at close time dealt with it. |
341 | */ | |
ef5e2b78 | 342 | if (dn_mark == new_dn_mark) |
3c5119c0 | 343 | destroy = 1; |
b3a00660 | 344 | error = 0; |
3c5119c0 EP |
345 | goto out; |
346 | } | |
1da177e4 | 347 | |
01919134 | 348 | __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0); |
3c5119c0 | 349 | |
ef5e2b78 EP |
350 | error = attach_dn(dn, dn_mark, id, fd, filp, mask); |
351 | /* !error means that we attached the dn to the dn_mark, so don't free it */ | |
3c5119c0 EP |
352 | if (!error) |
353 | dn = NULL; | |
354 | /* -EEXIST means that we didn't add this new dn and used an old one. | |
355 | * that isn't an error (and the unused dn should be freed) */ | |
356 | else if (error == -EEXIST) | |
357 | error = 0; | |
358 | ||
ef5e2b78 | 359 | dnotify_recalc_inode_mask(fsn_mark); |
3c5119c0 | 360 | out: |
ef5e2b78 | 361 | spin_unlock(&fsn_mark->lock); |
3c5119c0 EP |
362 | |
363 | if (destroy) | |
4712e722 | 364 | fsnotify_detach_mark(fsn_mark); |
52f85729 | 365 | mutex_unlock(&dnotify_group->mark_mutex); |
4712e722 JK |
366 | if (destroy) |
367 | fsnotify_free_mark(fsn_mark); | |
ef5e2b78 | 368 | fsnotify_put_mark(fsn_mark); |
3c5119c0 | 369 | out_err: |
ef5e2b78 EP |
370 | if (new_fsn_mark) |
371 | fsnotify_put_mark(new_fsn_mark); | |
3c5119c0 EP |
372 | if (dn) |
373 | kmem_cache_free(dnotify_struct_cache, dn); | |
374 | return error; | |
1da177e4 | 375 | } |
1da177e4 LT |
376 | |
377 | static int __init dnotify_init(void) | |
378 | { | |
d46eb14b SB |
379 | dnotify_struct_cache = KMEM_CACHE(dnotify_struct, |
380 | SLAB_PANIC|SLAB_ACCOUNT); | |
381 | dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC|SLAB_ACCOUNT); | |
3c5119c0 | 382 | |
0d2e2a1d | 383 | dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops); |
3c5119c0 EP |
384 | if (IS_ERR(dnotify_group)) |
385 | panic("unable to allocate fsnotify group for dnotify\n"); | |
1da177e4 LT |
386 | return 0; |
387 | } | |
388 | ||
389 | module_init(dnotify_init) |