xref: /linux/fs/notify/fanotify/fanotify.c (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/fanotify.h>
3 #include <linux/fdtable.h>
4 #include <linux/fsnotify_backend.h>
5 #include <linux/init.h>
6 #include <linux/jiffies.h>
7 #include <linux/kernel.h> /* UINT_MAX */
8 #include <linux/mount.h>
9 #include <linux/sched.h>
10 #include <linux/sched/user.h>
11 #include <linux/sched/signal.h>
12 #include <linux/types.h>
13 #include <linux/wait.h>
14 #include <linux/audit.h>
15 #include <linux/sched/mm.h>
16 #include <linux/statfs.h>
17 #include <linux/stringhash.h>
18 
19 #include "fanotify.h"
20 
fanotify_path_equal(const struct path * p1,const struct path * p2)21 static bool fanotify_path_equal(const struct path *p1, const struct path *p2)
22 {
23 	return p1->mnt == p2->mnt && p1->dentry == p2->dentry;
24 }
25 
fanotify_hash_path(const struct path * path)26 static unsigned int fanotify_hash_path(const struct path *path)
27 {
28 	return hash_ptr(path->dentry, FANOTIFY_EVENT_HASH_BITS) ^
29 		hash_ptr(path->mnt, FANOTIFY_EVENT_HASH_BITS);
30 }
31 
fanotify_hash_fsid(__kernel_fsid_t * fsid)32 static unsigned int fanotify_hash_fsid(__kernel_fsid_t *fsid)
33 {
34 	return hash_32(fsid->val[0], FANOTIFY_EVENT_HASH_BITS) ^
35 		hash_32(fsid->val[1], FANOTIFY_EVENT_HASH_BITS);
36 }
37 
fanotify_fh_equal(struct fanotify_fh * fh1,struct fanotify_fh * fh2)38 static bool fanotify_fh_equal(struct fanotify_fh *fh1,
39 			      struct fanotify_fh *fh2)
40 {
41 	if (fh1->type != fh2->type || fh1->len != fh2->len)
42 		return false;
43 
44 	return !fh1->len ||
45 		!memcmp(fanotify_fh_buf(fh1), fanotify_fh_buf(fh2), fh1->len);
46 }
47 
fanotify_hash_fh(struct fanotify_fh * fh)48 static unsigned int fanotify_hash_fh(struct fanotify_fh *fh)
49 {
50 	long salt = (long)fh->type | (long)fh->len << 8;
51 
52 	/*
53 	 * full_name_hash() works long by long, so it handles fh buf optimally.
54 	 */
55 	return full_name_hash((void *)salt, fanotify_fh_buf(fh), fh->len);
56 }
57 
fanotify_fid_event_equal(struct fanotify_fid_event * ffe1,struct fanotify_fid_event * ffe2)58 static bool fanotify_fid_event_equal(struct fanotify_fid_event *ffe1,
59 				     struct fanotify_fid_event *ffe2)
60 {
61 	/* Do not merge fid events without object fh */
62 	if (!ffe1->object_fh.len)
63 		return false;
64 
65 	return fanotify_fsid_equal(&ffe1->fsid, &ffe2->fsid) &&
66 		fanotify_fh_equal(&ffe1->object_fh, &ffe2->object_fh);
67 }
68 
fanotify_info_equal(struct fanotify_info * info1,struct fanotify_info * info2)69 static bool fanotify_info_equal(struct fanotify_info *info1,
70 				struct fanotify_info *info2)
71 {
72 	if (info1->dir_fh_totlen != info2->dir_fh_totlen ||
73 	    info1->dir2_fh_totlen != info2->dir2_fh_totlen ||
74 	    info1->file_fh_totlen != info2->file_fh_totlen ||
75 	    info1->name_len != info2->name_len ||
76 	    info1->name2_len != info2->name2_len)
77 		return false;
78 
79 	if (info1->dir_fh_totlen &&
80 	    !fanotify_fh_equal(fanotify_info_dir_fh(info1),
81 			       fanotify_info_dir_fh(info2)))
82 		return false;
83 
84 	if (info1->dir2_fh_totlen &&
85 	    !fanotify_fh_equal(fanotify_info_dir2_fh(info1),
86 			       fanotify_info_dir2_fh(info2)))
87 		return false;
88 
89 	if (info1->file_fh_totlen &&
90 	    !fanotify_fh_equal(fanotify_info_file_fh(info1),
91 			       fanotify_info_file_fh(info2)))
92 		return false;
93 
94 	if (info1->name_len &&
95 	    memcmp(fanotify_info_name(info1), fanotify_info_name(info2),
96 		   info1->name_len))
97 		return false;
98 
99 	return !info1->name2_len ||
100 		!memcmp(fanotify_info_name2(info1), fanotify_info_name2(info2),
101 			info1->name2_len);
102 }
103 
fanotify_name_event_equal(struct fanotify_name_event * fne1,struct fanotify_name_event * fne2)104 static bool fanotify_name_event_equal(struct fanotify_name_event *fne1,
105 				      struct fanotify_name_event *fne2)
106 {
107 	struct fanotify_info *info1 = &fne1->info;
108 	struct fanotify_info *info2 = &fne2->info;
109 
110 	/* Do not merge name events without dir fh */
111 	if (!info1->dir_fh_totlen)
112 		return false;
113 
114 	if (!fanotify_fsid_equal(&fne1->fsid, &fne2->fsid))
115 		return false;
116 
117 	return fanotify_info_equal(info1, info2);
118 }
119 
fanotify_error_event_equal(struct fanotify_error_event * fee1,struct fanotify_error_event * fee2)120 static bool fanotify_error_event_equal(struct fanotify_error_event *fee1,
121 				       struct fanotify_error_event *fee2)
122 {
123 	/* Error events against the same file system are always merged. */
124 	if (!fanotify_fsid_equal(&fee1->fsid, &fee2->fsid))
125 		return false;
126 
127 	return true;
128 }
129 
fanotify_should_merge(struct fanotify_event * old,struct fanotify_event * new)130 static bool fanotify_should_merge(struct fanotify_event *old,
131 				  struct fanotify_event *new)
132 {
133 	pr_debug("%s: old=%p new=%p\n", __func__, old, new);
134 
135 	if (old->hash != new->hash ||
136 	    old->type != new->type || old->pid != new->pid)
137 		return false;
138 
139 	/*
140 	 * We want to merge many dirent events in the same dir (i.e.
141 	 * creates/unlinks/renames), but we do not want to merge dirent
142 	 * events referring to subdirs with dirent events referring to
143 	 * non subdirs, otherwise, user won't be able to tell from a
144 	 * mask FAN_CREATE|FAN_DELETE|FAN_ONDIR if it describes mkdir+
145 	 * unlink pair or rmdir+create pair of events.
146 	 */
147 	if ((old->mask & FS_ISDIR) != (new->mask & FS_ISDIR))
148 		return false;
149 
150 	/*
151 	 * FAN_RENAME event is reported with special info record types,
152 	 * so we cannot merge it with other events.
153 	 */
154 	if ((old->mask & FAN_RENAME) != (new->mask & FAN_RENAME))
155 		return false;
156 
157 	switch (old->type) {
158 	case FANOTIFY_EVENT_TYPE_PATH:
159 		return fanotify_path_equal(fanotify_event_path(old),
160 					   fanotify_event_path(new));
161 	case FANOTIFY_EVENT_TYPE_FID:
162 		return fanotify_fid_event_equal(FANOTIFY_FE(old),
163 						FANOTIFY_FE(new));
164 	case FANOTIFY_EVENT_TYPE_FID_NAME:
165 		return fanotify_name_event_equal(FANOTIFY_NE(old),
166 						 FANOTIFY_NE(new));
167 	case FANOTIFY_EVENT_TYPE_FS_ERROR:
168 		return fanotify_error_event_equal(FANOTIFY_EE(old),
169 						  FANOTIFY_EE(new));
170 	default:
171 		WARN_ON_ONCE(1);
172 	}
173 
174 	return false;
175 }
176 
177 /* Limit event merges to limit CPU overhead per event */
178 #define FANOTIFY_MAX_MERGE_EVENTS 128
179 
180 /* and the list better be locked by something too! */
fanotify_merge(struct fsnotify_group * group,struct fsnotify_event * event)181 static int fanotify_merge(struct fsnotify_group *group,
182 			  struct fsnotify_event *event)
183 {
184 	struct fanotify_event *old, *new = FANOTIFY_E(event);
185 	unsigned int bucket = fanotify_event_hash_bucket(group, new);
186 	struct hlist_head *hlist = &group->fanotify_data.merge_hash[bucket];
187 	int i = 0;
188 
189 	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
190 		 group, event, bucket);
191 
192 	/*
193 	 * Don't merge a permission event with any other event so that we know
194 	 * the event structure we have created in fanotify_handle_event() is the
195 	 * one we should check for permission response.
196 	 */
197 	if (fanotify_is_perm_event(new->mask))
198 		return 0;
199 
200 	hlist_for_each_entry(old, hlist, merge_list) {
201 		if (++i > FANOTIFY_MAX_MERGE_EVENTS)
202 			break;
203 		if (fanotify_should_merge(old, new)) {
204 			old->mask |= new->mask;
205 
206 			if (fanotify_is_error_event(old->mask))
207 				FANOTIFY_EE(old)->err_count++;
208 
209 			return 1;
210 		}
211 	}
212 
213 	return 0;
214 }
215 
216 /*
217  * Wait for response to permission event. The function also takes care of
218  * freeing the permission event (or offloads that in case the wait is canceled
219  * by a signal). The function returns 0 in case access got allowed by userspace,
220  * -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case
221  * the wait got interrupted by a signal.
222  */
fanotify_get_response(struct fsnotify_group * group,struct fanotify_perm_event * event,struct fsnotify_iter_info * iter_info)223 static int fanotify_get_response(struct fsnotify_group *group,
224 				 struct fanotify_perm_event *event,
225 				 struct fsnotify_iter_info *iter_info)
226 {
227 	int ret;
228 
229 	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
230 
231 	ret = wait_event_state(group->fanotify_data.access_waitq,
232 				  event->state == FAN_EVENT_ANSWERED,
233 				  (TASK_KILLABLE|TASK_FREEZABLE));
234 
235 	/* Signal pending? */
236 	if (ret < 0) {
237 		spin_lock(&group->notification_lock);
238 		/* Event reported to userspace and no answer yet? */
239 		if (event->state == FAN_EVENT_REPORTED) {
240 			/* Event will get freed once userspace answers to it */
241 			event->state = FAN_EVENT_CANCELED;
242 			spin_unlock(&group->notification_lock);
243 			return ret;
244 		}
245 		/* Event not yet reported? Just remove it. */
246 		if (event->state == FAN_EVENT_INIT) {
247 			fsnotify_remove_queued_event(group, &event->fae.fse);
248 			/* Permission events are not supposed to be hashed */
249 			WARN_ON_ONCE(!hlist_unhashed(&event->fae.merge_list));
250 		}
251 		/*
252 		 * Event may be also answered in case signal delivery raced
253 		 * with wakeup. In that case we have nothing to do besides
254 		 * freeing the event and reporting error.
255 		 */
256 		spin_unlock(&group->notification_lock);
257 		goto out;
258 	}
259 
260 	/* userspace responded, convert to something usable */
261 	switch (event->response & FANOTIFY_RESPONSE_ACCESS) {
262 	case FAN_ALLOW:
263 		ret = 0;
264 		break;
265 	case FAN_DENY:
266 	default:
267 		ret = -EPERM;
268 	}
269 
270 	/* Check if the response should be audited */
271 	if (event->response & FAN_AUDIT)
272 		audit_fanotify(event->response & ~FAN_AUDIT,
273 			       &event->audit_rule);
274 
275 	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
276 		 group, event, ret);
277 out:
278 	fsnotify_destroy_event(group, &event->fae.fse);
279 
280 	return ret;
281 }
282 
283 /*
284  * This function returns a mask for an event that only contains the flags
285  * that have been specifically requested by the user. Flags that may have
286  * been included within the event mask, but have not been explicitly
287  * requested by the user, will not be present in the returned mask.
288  */
fanotify_group_event_mask(struct fsnotify_group * group,struct fsnotify_iter_info * iter_info,u32 * match_mask,u32 event_mask,const void * data,int data_type,struct inode * dir)289 static u32 fanotify_group_event_mask(struct fsnotify_group *group,
290 				     struct fsnotify_iter_info *iter_info,
291 				     u32 *match_mask, u32 event_mask,
292 				     const void *data, int data_type,
293 				     struct inode *dir)
294 {
295 	__u32 marks_mask = 0, marks_ignore_mask = 0;
296 	__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS |
297 				     FANOTIFY_EVENT_FLAGS;
298 	const struct path *path = fsnotify_data_path(data, data_type);
299 	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
300 	struct fsnotify_mark *mark;
301 	bool ondir = event_mask & FAN_ONDIR;
302 	int type;
303 
304 	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
305 		 __func__, iter_info->report_mask, event_mask, data, data_type);
306 
307 	if (!fid_mode) {
308 		/* Do we have path to open a file descriptor? */
309 		if (!path)
310 			return 0;
311 		/* Path type events are only relevant for files and dirs */
312 		if (!d_is_reg(path->dentry) && !d_can_lookup(path->dentry))
313 			return 0;
314 	} else if (!(fid_mode & FAN_REPORT_FID)) {
315 		/* Do we have a directory inode to report? */
316 		if (!dir && !ondir)
317 			return 0;
318 	}
319 
320 	fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
321 		/*
322 		 * Apply ignore mask depending on event flags in ignore mask.
323 		 */
324 		marks_ignore_mask |=
325 			fsnotify_effective_ignore_mask(mark, ondir, type);
326 
327 		/*
328 		 * Send the event depending on event flags in mark mask.
329 		 */
330 		if (!fsnotify_mask_applicable(mark->mask, ondir, type))
331 			continue;
332 
333 		marks_mask |= mark->mask;
334 
335 		/* Record the mark types of this group that matched the event */
336 		*match_mask |= 1U << type;
337 	}
338 
339 	test_mask = event_mask & marks_mask & ~marks_ignore_mask;
340 
341 	/*
342 	 * For dirent modification events (create/delete/move) that do not carry
343 	 * the child entry name information, we report FAN_ONDIR for mkdir/rmdir
344 	 * so user can differentiate them from creat/unlink.
345 	 *
346 	 * For backward compatibility and consistency, do not report FAN_ONDIR
347 	 * to user in legacy fanotify mode (reporting fd) and report FAN_ONDIR
348 	 * to user in fid mode for all event types.
349 	 *
350 	 * We never report FAN_EVENT_ON_CHILD to user, but we do pass it in to
351 	 * fanotify_alloc_event() when group is reporting fid as indication
352 	 * that event happened on child.
353 	 */
354 	if (fid_mode) {
355 		/* Do not report event flags without any event */
356 		if (!(test_mask & ~FANOTIFY_EVENT_FLAGS))
357 			return 0;
358 	} else {
359 		user_mask &= ~FANOTIFY_EVENT_FLAGS;
360 	}
361 
362 	return test_mask & user_mask;
363 }
364 
365 /*
366  * Check size needed to encode fanotify_fh.
367  *
368  * Return size of encoded fh without fanotify_fh header.
369  * Return 0 on failure to encode.
370  */
fanotify_encode_fh_len(struct inode * inode)371 static int fanotify_encode_fh_len(struct inode *inode)
372 {
373 	int dwords = 0;
374 	int fh_len;
375 
376 	if (!inode)
377 		return 0;
378 
379 	exportfs_encode_fid(inode, NULL, &dwords);
380 	fh_len = dwords << 2;
381 
382 	/*
383 	 * struct fanotify_error_event might be preallocated and is
384 	 * limited to MAX_HANDLE_SZ.  This should never happen, but
385 	 * safeguard by forcing an invalid file handle.
386 	 */
387 	if (WARN_ON_ONCE(fh_len > MAX_HANDLE_SZ))
388 		return 0;
389 
390 	return fh_len;
391 }
392 
393 /*
394  * Encode fanotify_fh.
395  *
396  * Return total size of encoded fh including fanotify_fh header.
397  * Return 0 on failure to encode.
398  */
fanotify_encode_fh(struct fanotify_fh * fh,struct inode * inode,unsigned int fh_len,unsigned int * hash,gfp_t gfp)399 static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
400 			      unsigned int fh_len, unsigned int *hash,
401 			      gfp_t gfp)
402 {
403 	int dwords, type = 0;
404 	char *ext_buf = NULL;
405 	void *buf = fh->buf;
406 	int err;
407 
408 	fh->type = FILEID_ROOT;
409 	fh->len = 0;
410 	fh->flags = 0;
411 
412 	/*
413 	 * Invalid FHs are used by FAN_FS_ERROR for errors not
414 	 * linked to any inode. The f_handle won't be reported
415 	 * back to userspace.
416 	 */
417 	if (!inode)
418 		goto out;
419 
420 	/*
421 	 * !gpf means preallocated variable size fh, but fh_len could
422 	 * be zero in that case if encoding fh len failed.
423 	 */
424 	err = -ENOENT;
425 	if (fh_len < 4 || WARN_ON_ONCE(fh_len % 4) || fh_len > MAX_HANDLE_SZ)
426 		goto out_err;
427 
428 	/* No external buffer in a variable size allocated fh */
429 	if (gfp && fh_len > FANOTIFY_INLINE_FH_LEN) {
430 		/* Treat failure to allocate fh as failure to encode fh */
431 		err = -ENOMEM;
432 		ext_buf = kmalloc(fh_len, gfp);
433 		if (!ext_buf)
434 			goto out_err;
435 
436 		*fanotify_fh_ext_buf_ptr(fh) = ext_buf;
437 		buf = ext_buf;
438 		fh->flags |= FANOTIFY_FH_FLAG_EXT_BUF;
439 	}
440 
441 	dwords = fh_len >> 2;
442 	type = exportfs_encode_fid(inode, buf, &dwords);
443 	err = -EINVAL;
444 	if (type <= 0 || type == FILEID_INVALID || fh_len != dwords << 2)
445 		goto out_err;
446 
447 	fh->type = type;
448 	fh->len = fh_len;
449 
450 out:
451 	/*
452 	 * Mix fh into event merge key.  Hash might be NULL in case of
453 	 * unhashed FID events (i.e. FAN_FS_ERROR).
454 	 */
455 	if (hash)
456 		*hash ^= fanotify_hash_fh(fh);
457 
458 	return FANOTIFY_FH_HDR_LEN + fh_len;
459 
460 out_err:
461 	pr_warn_ratelimited("fanotify: failed to encode fid (type=%d, len=%d, err=%i)\n",
462 			    type, fh_len, err);
463 	kfree(ext_buf);
464 	*fanotify_fh_ext_buf_ptr(fh) = NULL;
465 	/* Report the event without a file identifier on encode error */
466 	fh->type = FILEID_INVALID;
467 	fh->len = 0;
468 	return 0;
469 }
470 
471 /*
472  * FAN_REPORT_FID is ambiguous in that it reports the fid of the child for
473  * some events and the fid of the parent for create/delete/move events.
474  *
475  * With the FAN_REPORT_TARGET_FID flag, the fid of the child is reported
476  * also in create/delete/move events in addition to the fid of the parent
477  * and the name of the child.
478  */
fanotify_report_child_fid(unsigned int fid_mode,u32 mask)479 static inline bool fanotify_report_child_fid(unsigned int fid_mode, u32 mask)
480 {
481 	if (mask & ALL_FSNOTIFY_DIRENT_EVENTS)
482 		return (fid_mode & FAN_REPORT_TARGET_FID);
483 
484 	return (fid_mode & FAN_REPORT_FID) && !(mask & FAN_ONDIR);
485 }
486 
487 /*
488  * The inode to use as identifier when reporting fid depends on the event
489  * and the group flags.
490  *
491  * With the group flag FAN_REPORT_TARGET_FID, always report the child fid.
492  *
493  * Without the group flag FAN_REPORT_TARGET_FID, report the modified directory
494  * fid on dirent events and the child fid otherwise.
495  *
496  * For example:
497  * FS_ATTRIB reports the child fid even if reported on a watched parent.
498  * FS_CREATE reports the modified dir fid without FAN_REPORT_TARGET_FID.
499  *       and reports the created child fid with FAN_REPORT_TARGET_FID.
500  */
fanotify_fid_inode(u32 event_mask,const void * data,int data_type,struct inode * dir,unsigned int fid_mode)501 static struct inode *fanotify_fid_inode(u32 event_mask, const void *data,
502 					int data_type, struct inode *dir,
503 					unsigned int fid_mode)
504 {
505 	if ((event_mask & ALL_FSNOTIFY_DIRENT_EVENTS) &&
506 	    !(fid_mode & FAN_REPORT_TARGET_FID))
507 		return dir;
508 
509 	return fsnotify_data_inode(data, data_type);
510 }
511 
512 /*
513  * The inode to use as identifier when reporting dir fid depends on the event.
514  * Report the modified directory inode on dirent modification events.
515  * Report the "victim" inode if "victim" is a directory.
516  * Report the parent inode if "victim" is not a directory and event is
517  * reported to parent.
518  * Otherwise, do not report dir fid.
519  */
fanotify_dfid_inode(u32 event_mask,const void * data,int data_type,struct inode * dir)520 static struct inode *fanotify_dfid_inode(u32 event_mask, const void *data,
521 					 int data_type, struct inode *dir)
522 {
523 	struct inode *inode = fsnotify_data_inode(data, data_type);
524 
525 	if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
526 		return dir;
527 
528 	if (inode && S_ISDIR(inode->i_mode))
529 		return inode;
530 
531 	return dir;
532 }
533 
fanotify_alloc_path_event(const struct path * path,unsigned int * hash,gfp_t gfp)534 static struct fanotify_event *fanotify_alloc_path_event(const struct path *path,
535 							unsigned int *hash,
536 							gfp_t gfp)
537 {
538 	struct fanotify_path_event *pevent;
539 
540 	pevent = kmem_cache_alloc(fanotify_path_event_cachep, gfp);
541 	if (!pevent)
542 		return NULL;
543 
544 	pevent->fae.type = FANOTIFY_EVENT_TYPE_PATH;
545 	pevent->path = *path;
546 	*hash ^= fanotify_hash_path(path);
547 	path_get(path);
548 
549 	return &pevent->fae;
550 }
551 
fanotify_alloc_perm_event(const struct path * path,gfp_t gfp)552 static struct fanotify_event *fanotify_alloc_perm_event(const struct path *path,
553 							gfp_t gfp)
554 {
555 	struct fanotify_perm_event *pevent;
556 
557 	pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
558 	if (!pevent)
559 		return NULL;
560 
561 	pevent->fae.type = FANOTIFY_EVENT_TYPE_PATH_PERM;
562 	pevent->response = 0;
563 	pevent->hdr.type = FAN_RESPONSE_INFO_NONE;
564 	pevent->hdr.pad = 0;
565 	pevent->hdr.len = 0;
566 	pevent->state = FAN_EVENT_INIT;
567 	pevent->path = *path;
568 	path_get(path);
569 
570 	return &pevent->fae;
571 }
572 
fanotify_alloc_fid_event(struct inode * id,__kernel_fsid_t * fsid,unsigned int * hash,gfp_t gfp)573 static struct fanotify_event *fanotify_alloc_fid_event(struct inode *id,
574 						       __kernel_fsid_t *fsid,
575 						       unsigned int *hash,
576 						       gfp_t gfp)
577 {
578 	struct fanotify_fid_event *ffe;
579 
580 	ffe = kmem_cache_alloc(fanotify_fid_event_cachep, gfp);
581 	if (!ffe)
582 		return NULL;
583 
584 	ffe->fae.type = FANOTIFY_EVENT_TYPE_FID;
585 	ffe->fsid = *fsid;
586 	*hash ^= fanotify_hash_fsid(fsid);
587 	fanotify_encode_fh(&ffe->object_fh, id, fanotify_encode_fh_len(id),
588 			   hash, gfp);
589 
590 	return &ffe->fae;
591 }
592 
fanotify_alloc_name_event(struct inode * dir,__kernel_fsid_t * fsid,const struct qstr * name,struct inode * child,struct dentry * moved,unsigned int * hash,gfp_t gfp)593 static struct fanotify_event *fanotify_alloc_name_event(struct inode *dir,
594 							__kernel_fsid_t *fsid,
595 							const struct qstr *name,
596 							struct inode *child,
597 							struct dentry *moved,
598 							unsigned int *hash,
599 							gfp_t gfp)
600 {
601 	struct fanotify_name_event *fne;
602 	struct fanotify_info *info;
603 	struct fanotify_fh *dfh, *ffh;
604 	struct inode *dir2 = moved ? d_inode(moved->d_parent) : NULL;
605 	const struct qstr *name2 = moved ? &moved->d_name : NULL;
606 	unsigned int dir_fh_len = fanotify_encode_fh_len(dir);
607 	unsigned int dir2_fh_len = fanotify_encode_fh_len(dir2);
608 	unsigned int child_fh_len = fanotify_encode_fh_len(child);
609 	unsigned long name_len = name ? name->len : 0;
610 	unsigned long name2_len = name2 ? name2->len : 0;
611 	unsigned int len, size;
612 
613 	/* Reserve terminating null byte even for empty name */
614 	size = sizeof(*fne) + name_len + name2_len + 2;
615 	if (dir_fh_len)
616 		size += FANOTIFY_FH_HDR_LEN + dir_fh_len;
617 	if (dir2_fh_len)
618 		size += FANOTIFY_FH_HDR_LEN + dir2_fh_len;
619 	if (child_fh_len)
620 		size += FANOTIFY_FH_HDR_LEN + child_fh_len;
621 	fne = kmalloc(size, gfp);
622 	if (!fne)
623 		return NULL;
624 
625 	fne->fae.type = FANOTIFY_EVENT_TYPE_FID_NAME;
626 	fne->fsid = *fsid;
627 	*hash ^= fanotify_hash_fsid(fsid);
628 	info = &fne->info;
629 	fanotify_info_init(info);
630 	if (dir_fh_len) {
631 		dfh = fanotify_info_dir_fh(info);
632 		len = fanotify_encode_fh(dfh, dir, dir_fh_len, hash, 0);
633 		fanotify_info_set_dir_fh(info, len);
634 	}
635 	if (dir2_fh_len) {
636 		dfh = fanotify_info_dir2_fh(info);
637 		len = fanotify_encode_fh(dfh, dir2, dir2_fh_len, hash, 0);
638 		fanotify_info_set_dir2_fh(info, len);
639 	}
640 	if (child_fh_len) {
641 		ffh = fanotify_info_file_fh(info);
642 		len = fanotify_encode_fh(ffh, child, child_fh_len, hash, 0);
643 		fanotify_info_set_file_fh(info, len);
644 	}
645 	if (name_len) {
646 		fanotify_info_copy_name(info, name);
647 		*hash ^= full_name_hash((void *)name_len, name->name, name_len);
648 	}
649 	if (name2_len) {
650 		fanotify_info_copy_name2(info, name2);
651 		*hash ^= full_name_hash((void *)name2_len, name2->name,
652 					name2_len);
653 	}
654 
655 	pr_debug("%s: size=%u dir_fh_len=%u child_fh_len=%u name_len=%u name='%.*s'\n",
656 		 __func__, size, dir_fh_len, child_fh_len,
657 		 info->name_len, info->name_len, fanotify_info_name(info));
658 
659 	if (dir2_fh_len) {
660 		pr_debug("%s: dir2_fh_len=%u name2_len=%u name2='%.*s'\n",
661 			 __func__, dir2_fh_len, info->name2_len,
662 			 info->name2_len, fanotify_info_name2(info));
663 	}
664 
665 	return &fne->fae;
666 }
667 
fanotify_alloc_error_event(struct fsnotify_group * group,__kernel_fsid_t * fsid,const void * data,int data_type,unsigned int * hash)668 static struct fanotify_event *fanotify_alloc_error_event(
669 						struct fsnotify_group *group,
670 						__kernel_fsid_t *fsid,
671 						const void *data, int data_type,
672 						unsigned int *hash)
673 {
674 	struct fs_error_report *report =
675 			fsnotify_data_error_report(data, data_type);
676 	struct inode *inode;
677 	struct fanotify_error_event *fee;
678 	int fh_len;
679 
680 	if (WARN_ON_ONCE(!report))
681 		return NULL;
682 
683 	fee = mempool_alloc(&group->fanotify_data.error_events_pool, GFP_NOFS);
684 	if (!fee)
685 		return NULL;
686 
687 	fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
688 	fee->error = report->error;
689 	fee->err_count = 1;
690 	fee->fsid = *fsid;
691 
692 	inode = report->inode;
693 	fh_len = fanotify_encode_fh_len(inode);
694 
695 	/* Bad fh_len. Fallback to using an invalid fh. Should never happen. */
696 	if (!fh_len && inode)
697 		inode = NULL;
698 
699 	fanotify_encode_fh(&fee->object_fh, inode, fh_len, NULL, 0);
700 
701 	*hash ^= fanotify_hash_fsid(fsid);
702 
703 	return &fee->fae;
704 }
705 
fanotify_alloc_event(struct fsnotify_group * group,u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,__kernel_fsid_t * fsid,u32 match_mask)706 static struct fanotify_event *fanotify_alloc_event(
707 				struct fsnotify_group *group,
708 				u32 mask, const void *data, int data_type,
709 				struct inode *dir, const struct qstr *file_name,
710 				__kernel_fsid_t *fsid, u32 match_mask)
711 {
712 	struct fanotify_event *event = NULL;
713 	gfp_t gfp = GFP_KERNEL_ACCOUNT;
714 	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
715 	struct inode *id = fanotify_fid_inode(mask, data, data_type, dir,
716 					      fid_mode);
717 	struct inode *dirid = fanotify_dfid_inode(mask, data, data_type, dir);
718 	const struct path *path = fsnotify_data_path(data, data_type);
719 	struct mem_cgroup *old_memcg;
720 	struct dentry *moved = NULL;
721 	struct inode *child = NULL;
722 	bool name_event = false;
723 	unsigned int hash = 0;
724 	bool ondir = mask & FAN_ONDIR;
725 	struct pid *pid;
726 
727 	if ((fid_mode & FAN_REPORT_DIR_FID) && dirid) {
728 		/*
729 		 * For certain events and group flags, report the child fid
730 		 * in addition to reporting the parent fid and maybe child name.
731 		 */
732 		if (fanotify_report_child_fid(fid_mode, mask) && id != dirid)
733 			child = id;
734 
735 		id = dirid;
736 
737 		/*
738 		 * We record file name only in a group with FAN_REPORT_NAME
739 		 * and when we have a directory inode to report.
740 		 *
741 		 * For directory entry modification event, we record the fid of
742 		 * the directory and the name of the modified entry.
743 		 *
744 		 * For event on non-directory that is reported to parent, we
745 		 * record the fid of the parent and the name of the child.
746 		 *
747 		 * Even if not reporting name, we need a variable length
748 		 * fanotify_name_event if reporting both parent and child fids.
749 		 */
750 		if (!(fid_mode & FAN_REPORT_NAME)) {
751 			name_event = !!child;
752 			file_name = NULL;
753 		} else if ((mask & ALL_FSNOTIFY_DIRENT_EVENTS) || !ondir) {
754 			name_event = true;
755 		}
756 
757 		/*
758 		 * In the special case of FAN_RENAME event, use the match_mask
759 		 * to determine if we need to report only the old parent+name,
760 		 * only the new parent+name or both.
761 		 * 'dirid' and 'file_name' are the old parent+name and
762 		 * 'moved' has the new parent+name.
763 		 */
764 		if (mask & FAN_RENAME) {
765 			bool report_old, report_new;
766 
767 			if (WARN_ON_ONCE(!match_mask))
768 				return NULL;
769 
770 			/* Report both old and new parent+name if sb watching */
771 			report_old = report_new =
772 				match_mask & (1U << FSNOTIFY_ITER_TYPE_SB);
773 			report_old |=
774 				match_mask & (1U << FSNOTIFY_ITER_TYPE_INODE);
775 			report_new |=
776 				match_mask & (1U << FSNOTIFY_ITER_TYPE_INODE2);
777 
778 			if (!report_old) {
779 				/* Do not report old parent+name */
780 				dirid = NULL;
781 				file_name = NULL;
782 			}
783 			if (report_new) {
784 				/* Report new parent+name */
785 				moved = fsnotify_data_dentry(data, data_type);
786 			}
787 		}
788 	}
789 
790 	/*
791 	 * For queues with unlimited length lost events are not expected and
792 	 * can possibly have security implications. Avoid losing events when
793 	 * memory is short. For the limited size queues, avoid OOM killer in the
794 	 * target monitoring memcg as it may have security repercussion.
795 	 */
796 	if (group->max_events == UINT_MAX)
797 		gfp |= __GFP_NOFAIL;
798 	else
799 		gfp |= __GFP_RETRY_MAYFAIL;
800 
801 	/* Whoever is interested in the event, pays for the allocation. */
802 	old_memcg = set_active_memcg(group->memcg);
803 
804 	if (fanotify_is_perm_event(mask)) {
805 		event = fanotify_alloc_perm_event(path, gfp);
806 	} else if (fanotify_is_error_event(mask)) {
807 		event = fanotify_alloc_error_event(group, fsid, data,
808 						   data_type, &hash);
809 	} else if (name_event && (file_name || moved || child)) {
810 		event = fanotify_alloc_name_event(dirid, fsid, file_name, child,
811 						  moved, &hash, gfp);
812 	} else if (fid_mode) {
813 		event = fanotify_alloc_fid_event(id, fsid, &hash, gfp);
814 	} else {
815 		event = fanotify_alloc_path_event(path, &hash, gfp);
816 	}
817 
818 	if (!event)
819 		goto out;
820 
821 	if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
822 		pid = get_pid(task_pid(current));
823 	else
824 		pid = get_pid(task_tgid(current));
825 
826 	/* Mix event info, FAN_ONDIR flag and pid into event merge key */
827 	hash ^= hash_long((unsigned long)pid | ondir, FANOTIFY_EVENT_HASH_BITS);
828 	fanotify_init_event(event, hash, mask);
829 	event->pid = pid;
830 
831 out:
832 	set_active_memcg(old_memcg);
833 	return event;
834 }
835 
836 /*
837  * Get cached fsid of the filesystem containing the object from any mark.
838  * All marks are supposed to have the same fsid, but we do not verify that here.
839  */
fanotify_get_fsid(struct fsnotify_iter_info * iter_info)840 static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
841 {
842 	struct fsnotify_mark *mark;
843 	int type;
844 	__kernel_fsid_t fsid = {};
845 
846 	fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
847 		if (!(mark->flags & FSNOTIFY_MARK_FLAG_HAS_FSID))
848 			continue;
849 		fsid = FANOTIFY_MARK(mark)->fsid;
850 		if (!(mark->flags & FSNOTIFY_MARK_FLAG_WEAK_FSID) &&
851 		    WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
852 			continue;
853 		return fsid;
854 	}
855 
856 	return fsid;
857 }
858 
859 /*
860  * Add an event to hash table for faster merge.
861  */
fanotify_insert_event(struct fsnotify_group * group,struct fsnotify_event * fsn_event)862 static void fanotify_insert_event(struct fsnotify_group *group,
863 				  struct fsnotify_event *fsn_event)
864 {
865 	struct fanotify_event *event = FANOTIFY_E(fsn_event);
866 	unsigned int bucket = fanotify_event_hash_bucket(group, event);
867 	struct hlist_head *hlist = &group->fanotify_data.merge_hash[bucket];
868 
869 	assert_spin_locked(&group->notification_lock);
870 
871 	if (!fanotify_is_hashed_event(event->mask))
872 		return;
873 
874 	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
875 		 group, event, bucket);
876 
877 	hlist_add_head(&event->merge_list, hlist);
878 }
879 
fanotify_handle_event(struct fsnotify_group * group,u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * file_name,u32 cookie,struct fsnotify_iter_info * iter_info)880 static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
881 				 const void *data, int data_type,
882 				 struct inode *dir,
883 				 const struct qstr *file_name, u32 cookie,
884 				 struct fsnotify_iter_info *iter_info)
885 {
886 	int ret = 0;
887 	struct fanotify_event *event;
888 	struct fsnotify_event *fsn_event;
889 	__kernel_fsid_t fsid = {};
890 	u32 match_mask = 0;
891 
892 	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
893 	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
894 	BUILD_BUG_ON(FAN_ATTRIB != FS_ATTRIB);
895 	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
896 	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
897 	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
898 	BUILD_BUG_ON(FAN_MOVED_TO != FS_MOVED_TO);
899 	BUILD_BUG_ON(FAN_MOVED_FROM != FS_MOVED_FROM);
900 	BUILD_BUG_ON(FAN_CREATE != FS_CREATE);
901 	BUILD_BUG_ON(FAN_DELETE != FS_DELETE);
902 	BUILD_BUG_ON(FAN_DELETE_SELF != FS_DELETE_SELF);
903 	BUILD_BUG_ON(FAN_MOVE_SELF != FS_MOVE_SELF);
904 	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
905 	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
906 	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
907 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
908 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
909 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
910 	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
911 	BUILD_BUG_ON(FAN_FS_ERROR != FS_ERROR);
912 	BUILD_BUG_ON(FAN_RENAME != FS_RENAME);
913 
914 	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 21);
915 
916 	mask = fanotify_group_event_mask(group, iter_info, &match_mask,
917 					 mask, data, data_type, dir);
918 	if (!mask)
919 		return 0;
920 
921 	pr_debug("%s: group=%p mask=%x report_mask=%x\n", __func__,
922 		 group, mask, match_mask);
923 
924 	if (fanotify_is_perm_event(mask)) {
925 		/*
926 		 * fsnotify_prepare_user_wait() fails if we race with mark
927 		 * deletion.  Just let the operation pass in that case.
928 		 */
929 		if (!fsnotify_prepare_user_wait(iter_info))
930 			return 0;
931 	}
932 
933 	if (FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS))
934 		fsid = fanotify_get_fsid(iter_info);
935 
936 	event = fanotify_alloc_event(group, mask, data, data_type, dir,
937 				     file_name, &fsid, match_mask);
938 	ret = -ENOMEM;
939 	if (unlikely(!event)) {
940 		/*
941 		 * We don't queue overflow events for permission events as
942 		 * there the access is denied and so no event is in fact lost.
943 		 */
944 		if (!fanotify_is_perm_event(mask))
945 			fsnotify_queue_overflow(group);
946 		goto finish;
947 	}
948 
949 	fsn_event = &event->fse;
950 	ret = fsnotify_insert_event(group, fsn_event, fanotify_merge,
951 				    fanotify_insert_event);
952 	if (ret) {
953 		/* Permission events shouldn't be merged */
954 		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
955 		/* Our event wasn't used in the end. Free it. */
956 		fsnotify_destroy_event(group, fsn_event);
957 
958 		ret = 0;
959 	} else if (fanotify_is_perm_event(mask)) {
960 		ret = fanotify_get_response(group, FANOTIFY_PERM(event),
961 					    iter_info);
962 	}
963 finish:
964 	if (fanotify_is_perm_event(mask))
965 		fsnotify_finish_user_wait(iter_info);
966 
967 	return ret;
968 }
969 
fanotify_free_group_priv(struct fsnotify_group * group)970 static void fanotify_free_group_priv(struct fsnotify_group *group)
971 {
972 	kfree(group->fanotify_data.merge_hash);
973 	if (group->fanotify_data.ucounts)
974 		dec_ucount(group->fanotify_data.ucounts,
975 			   UCOUNT_FANOTIFY_GROUPS);
976 
977 	if (mempool_initialized(&group->fanotify_data.error_events_pool))
978 		mempool_exit(&group->fanotify_data.error_events_pool);
979 }
980 
fanotify_free_path_event(struct fanotify_event * event)981 static void fanotify_free_path_event(struct fanotify_event *event)
982 {
983 	path_put(fanotify_event_path(event));
984 	kmem_cache_free(fanotify_path_event_cachep, FANOTIFY_PE(event));
985 }
986 
fanotify_free_perm_event(struct fanotify_event * event)987 static void fanotify_free_perm_event(struct fanotify_event *event)
988 {
989 	path_put(fanotify_event_path(event));
990 	kmem_cache_free(fanotify_perm_event_cachep, FANOTIFY_PERM(event));
991 }
992 
fanotify_free_fid_event(struct fanotify_event * event)993 static void fanotify_free_fid_event(struct fanotify_event *event)
994 {
995 	struct fanotify_fid_event *ffe = FANOTIFY_FE(event);
996 
997 	if (fanotify_fh_has_ext_buf(&ffe->object_fh))
998 		kfree(fanotify_fh_ext_buf(&ffe->object_fh));
999 	kmem_cache_free(fanotify_fid_event_cachep, ffe);
1000 }
1001 
fanotify_free_name_event(struct fanotify_event * event)1002 static void fanotify_free_name_event(struct fanotify_event *event)
1003 {
1004 	kfree(FANOTIFY_NE(event));
1005 }
1006 
fanotify_free_error_event(struct fsnotify_group * group,struct fanotify_event * event)1007 static void fanotify_free_error_event(struct fsnotify_group *group,
1008 				      struct fanotify_event *event)
1009 {
1010 	struct fanotify_error_event *fee = FANOTIFY_EE(event);
1011 
1012 	mempool_free(fee, &group->fanotify_data.error_events_pool);
1013 }
1014 
fanotify_free_event(struct fsnotify_group * group,struct fsnotify_event * fsn_event)1015 static void fanotify_free_event(struct fsnotify_group *group,
1016 				struct fsnotify_event *fsn_event)
1017 {
1018 	struct fanotify_event *event;
1019 
1020 	event = FANOTIFY_E(fsn_event);
1021 	put_pid(event->pid);
1022 	switch (event->type) {
1023 	case FANOTIFY_EVENT_TYPE_PATH:
1024 		fanotify_free_path_event(event);
1025 		break;
1026 	case FANOTIFY_EVENT_TYPE_PATH_PERM:
1027 		fanotify_free_perm_event(event);
1028 		break;
1029 	case FANOTIFY_EVENT_TYPE_FID:
1030 		fanotify_free_fid_event(event);
1031 		break;
1032 	case FANOTIFY_EVENT_TYPE_FID_NAME:
1033 		fanotify_free_name_event(event);
1034 		break;
1035 	case FANOTIFY_EVENT_TYPE_OVERFLOW:
1036 		kfree(event);
1037 		break;
1038 	case FANOTIFY_EVENT_TYPE_FS_ERROR:
1039 		fanotify_free_error_event(group, event);
1040 		break;
1041 	default:
1042 		WARN_ON_ONCE(1);
1043 	}
1044 }
1045 
fanotify_freeing_mark(struct fsnotify_mark * mark,struct fsnotify_group * group)1046 static void fanotify_freeing_mark(struct fsnotify_mark *mark,
1047 				  struct fsnotify_group *group)
1048 {
1049 	if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS))
1050 		dec_ucount(group->fanotify_data.ucounts, UCOUNT_FANOTIFY_MARKS);
1051 }
1052 
fanotify_free_mark(struct fsnotify_mark * fsn_mark)1053 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
1054 {
1055 	kmem_cache_free(fanotify_mark_cache, FANOTIFY_MARK(fsn_mark));
1056 }
1057 
1058 const struct fsnotify_ops fanotify_fsnotify_ops = {
1059 	.handle_event = fanotify_handle_event,
1060 	.free_group_priv = fanotify_free_group_priv,
1061 	.free_event = fanotify_free_event,
1062 	.freeing_mark = fanotify_freeing_mark,
1063 	.free_mark = fanotify_free_mark,
1064 };
1065