1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/fanotify.h>
3 #include <linux/fcntl.h>
4 #include <linux/fdtable.h>
5 #include <linux/file.h>
6 #include <linux/fs.h>
7 #include <linux/anon_inodes.h>
8 #include <linux/fsnotify_backend.h>
9 #include <linux/init.h>
10 #include <linux/mount.h>
11 #include <linux/namei.h>
12 #include <linux/poll.h>
13 #include <linux/security.h>
14 #include <linux/syscalls.h>
15 #include <linux/slab.h>
16 #include <linux/types.h>
17 #include <linux/uaccess.h>
18 #include <linux/compat.h>
19 #include <linux/sched/signal.h>
20 #include <linux/memcontrol.h>
21 #include <linux/statfs.h>
22 #include <linux/exportfs.h>
23 
24 #include <asm/ioctls.h>
25 
26 #include "../../mount.h"
27 #include "../fdinfo.h"
28 #include "fanotify.h"
29 
30 #define FANOTIFY_DEFAULT_MAX_EVENTS	16384
31 #define FANOTIFY_OLD_DEFAULT_MAX_MARKS	8192
32 #define FANOTIFY_DEFAULT_MAX_GROUPS	128
33 #define FANOTIFY_DEFAULT_FEE_POOL_SIZE	32
34 
35 /*
36  * Legacy fanotify marks limits (8192) is per group and we introduced a tunable
37  * limit of marks per user, similar to inotify.  Effectively, the legacy limit
38  * of fanotify marks per user is <max marks per group> * <max groups per user>.
39  * This default limit (1M) also happens to match the increased limit of inotify
40  * max_user_watches since v5.10.
41  */
42 #define FANOTIFY_DEFAULT_MAX_USER_MARKS	\
43 	(FANOTIFY_OLD_DEFAULT_MAX_MARKS * FANOTIFY_DEFAULT_MAX_GROUPS)
44 
45 /*
46  * Most of the memory cost of adding an inode mark is pinning the marked inode.
47  * The size of the filesystem inode struct is not uniform across filesystems,
48  * so double the size of a VFS inode is used as a conservative approximation.
49  */
50 #define INODE_MARK_COST	(2 * sizeof(struct inode))
51 
52 /* configurable via /proc/sys/fs/fanotify/ */
53 static int fanotify_max_queued_events __read_mostly;
54 
55 #ifdef CONFIG_SYSCTL
56 
57 #include <linux/sysctl.h>
58 
59 static long ft_zero = 0;
60 static long ft_int_max = INT_MAX;
61 
62 static struct ctl_table fanotify_table[] = {
63 	{
64 		.procname	= "max_user_groups",
65 		.data	= &init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS],
66 		.maxlen		= sizeof(long),
67 		.mode		= 0644,
68 		.proc_handler	= proc_doulongvec_minmax,
69 		.extra1		= &ft_zero,
70 		.extra2		= &ft_int_max,
71 	},
72 	{
73 		.procname	= "max_user_marks",
74 		.data	= &init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS],
75 		.maxlen		= sizeof(long),
76 		.mode		= 0644,
77 		.proc_handler	= proc_doulongvec_minmax,
78 		.extra1		= &ft_zero,
79 		.extra2		= &ft_int_max,
80 	},
81 	{
82 		.procname	= "max_queued_events",
83 		.data		= &fanotify_max_queued_events,
84 		.maxlen		= sizeof(int),
85 		.mode		= 0644,
86 		.proc_handler	= proc_dointvec_minmax,
87 		.extra1		= SYSCTL_ZERO
88 	},
89 	{ }
90 };
91 
fanotify_sysctls_init(void)92 static void __init fanotify_sysctls_init(void)
93 {
94 	register_sysctl("fs/fanotify", fanotify_table);
95 }
96 #else
97 #define fanotify_sysctls_init() do { } while (0)
98 #endif /* CONFIG_SYSCTL */
99 
100 /*
101  * All flags that may be specified in parameter event_f_flags of fanotify_init.
102  *
103  * Internal and external open flags are stored together in field f_flags of
104  * struct file. Only external open flags shall be allowed in event_f_flags.
105  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
106  * excluded.
107  */
108 #define	FANOTIFY_INIT_ALL_EVENT_F_BITS				( \
109 		O_ACCMODE	| O_APPEND	| O_NONBLOCK	| \
110 		__O_SYNC	| O_DSYNC	| O_CLOEXEC     | \
111 		O_LARGEFILE	| O_NOATIME	)
112 
113 extern const struct fsnotify_ops fanotify_fsnotify_ops;
114 
115 struct kmem_cache *fanotify_mark_cache __read_mostly;
116 struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
117 struct kmem_cache *fanotify_path_event_cachep __read_mostly;
118 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
119 
120 #define FANOTIFY_EVENT_ALIGN 4
121 #define FANOTIFY_FID_INFO_HDR_LEN \
122 	(sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
123 #define FANOTIFY_PIDFD_INFO_HDR_LEN \
124 	sizeof(struct fanotify_event_info_pidfd)
125 #define FANOTIFY_ERROR_INFO_LEN \
126 	(sizeof(struct fanotify_event_info_error))
127 
fanotify_fid_info_len(int fh_len,int name_len)128 static int fanotify_fid_info_len(int fh_len, int name_len)
129 {
130 	int info_len = fh_len;
131 
132 	if (name_len)
133 		info_len += name_len + 1;
134 
135 	return roundup(FANOTIFY_FID_INFO_HDR_LEN + info_len,
136 		       FANOTIFY_EVENT_ALIGN);
137 }
138 
139 /* FAN_RENAME may have one or two dir+name info records */
fanotify_dir_name_info_len(struct fanotify_event * event)140 static int fanotify_dir_name_info_len(struct fanotify_event *event)
141 {
142 	struct fanotify_info *info = fanotify_event_info(event);
143 	int dir_fh_len = fanotify_event_dir_fh_len(event);
144 	int dir2_fh_len = fanotify_event_dir2_fh_len(event);
145 	int info_len = 0;
146 
147 	if (dir_fh_len)
148 		info_len += fanotify_fid_info_len(dir_fh_len,
149 						  info->name_len);
150 	if (dir2_fh_len)
151 		info_len += fanotify_fid_info_len(dir2_fh_len,
152 						  info->name2_len);
153 
154 	return info_len;
155 }
156 
fanotify_event_len(unsigned int info_mode,struct fanotify_event * event)157 static size_t fanotify_event_len(unsigned int info_mode,
158 				 struct fanotify_event *event)
159 {
160 	size_t event_len = FAN_EVENT_METADATA_LEN;
161 	int fh_len;
162 	int dot_len = 0;
163 
164 	if (!info_mode)
165 		return event_len;
166 
167 	if (fanotify_is_error_event(event->mask))
168 		event_len += FANOTIFY_ERROR_INFO_LEN;
169 
170 	if (fanotify_event_has_any_dir_fh(event)) {
171 		event_len += fanotify_dir_name_info_len(event);
172 	} else if ((info_mode & FAN_REPORT_NAME) &&
173 		   (event->mask & FAN_ONDIR)) {
174 		/*
175 		 * With group flag FAN_REPORT_NAME, if name was not recorded in
176 		 * event on a directory, we will report the name ".".
177 		 */
178 		dot_len = 1;
179 	}
180 
181 	if (info_mode & FAN_REPORT_PIDFD)
182 		event_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
183 
184 	if (fanotify_event_has_object_fh(event)) {
185 		fh_len = fanotify_event_object_fh_len(event);
186 		event_len += fanotify_fid_info_len(fh_len, dot_len);
187 	}
188 
189 	return event_len;
190 }
191 
192 /*
193  * Remove an hashed event from merge hash table.
194  */
fanotify_unhash_event(struct fsnotify_group * group,struct fanotify_event * event)195 static void fanotify_unhash_event(struct fsnotify_group *group,
196 				  struct fanotify_event *event)
197 {
198 	assert_spin_locked(&group->notification_lock);
199 
200 	pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
201 		 group, event, fanotify_event_hash_bucket(group, event));
202 
203 	if (WARN_ON_ONCE(hlist_unhashed(&event->merge_list)))
204 		return;
205 
206 	hlist_del_init(&event->merge_list);
207 }
208 
209 /*
210  * Get an fanotify notification event if one exists and is small
211  * enough to fit in "count". Return an error pointer if the count
212  * is not large enough. When permission event is dequeued, its state is
213  * updated accordingly.
214  */
get_one_event(struct fsnotify_group * group,size_t count)215 static struct fanotify_event *get_one_event(struct fsnotify_group *group,
216 					    size_t count)
217 {
218 	size_t event_size;
219 	struct fanotify_event *event = NULL;
220 	struct fsnotify_event *fsn_event;
221 	unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
222 
223 	pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
224 
225 	spin_lock(&group->notification_lock);
226 	fsn_event = fsnotify_peek_first_event(group);
227 	if (!fsn_event)
228 		goto out;
229 
230 	event = FANOTIFY_E(fsn_event);
231 	event_size = fanotify_event_len(info_mode, event);
232 
233 	if (event_size > count) {
234 		event = ERR_PTR(-EINVAL);
235 		goto out;
236 	}
237 
238 	/*
239 	 * Held the notification_lock the whole time, so this is the
240 	 * same event we peeked above.
241 	 */
242 	fsnotify_remove_first_event(group);
243 	if (fanotify_is_perm_event(event->mask))
244 		FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
245 	if (fanotify_is_hashed_event(event->mask))
246 		fanotify_unhash_event(group, event);
247 out:
248 	spin_unlock(&group->notification_lock);
249 	return event;
250 }
251 
create_fd(struct fsnotify_group * group,const struct path * path,struct file ** file)252 static int create_fd(struct fsnotify_group *group, const struct path *path,
253 		     struct file **file)
254 {
255 	int client_fd;
256 	struct file *new_file;
257 
258 	client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
259 	if (client_fd < 0)
260 		return client_fd;
261 
262 	/*
263 	 * we need a new file handle for the userspace program so it can read even if it was
264 	 * originally opened O_WRONLY.
265 	 */
266 	new_file = dentry_open(path,
267 			       group->fanotify_data.f_flags | __FMODE_NONOTIFY,
268 			       current_cred());
269 	if (IS_ERR(new_file)) {
270 		/*
271 		 * we still send an event even if we can't open the file.  this
272 		 * can happen when say tasks are gone and we try to open their
273 		 * /proc files or we try to open a WRONLY file like in sysfs
274 		 * we just send the errno to userspace since there isn't much
275 		 * else we can do.
276 		 */
277 		put_unused_fd(client_fd);
278 		client_fd = PTR_ERR(new_file);
279 	} else {
280 		*file = new_file;
281 	}
282 
283 	return client_fd;
284 }
285 
process_access_response_info(const char __user * info,size_t info_len,struct fanotify_response_info_audit_rule * friar)286 static int process_access_response_info(const char __user *info,
287 					size_t info_len,
288 				struct fanotify_response_info_audit_rule *friar)
289 {
290 	if (info_len != sizeof(*friar))
291 		return -EINVAL;
292 
293 	if (copy_from_user(friar, info, sizeof(*friar)))
294 		return -EFAULT;
295 
296 	if (friar->hdr.type != FAN_RESPONSE_INFO_AUDIT_RULE)
297 		return -EINVAL;
298 	if (friar->hdr.pad != 0)
299 		return -EINVAL;
300 	if (friar->hdr.len != sizeof(*friar))
301 		return -EINVAL;
302 
303 	return info_len;
304 }
305 
306 /*
307  * Finish processing of permission event by setting it to ANSWERED state and
308  * drop group->notification_lock.
309  */
finish_permission_event(struct fsnotify_group * group,struct fanotify_perm_event * event,u32 response,struct fanotify_response_info_audit_rule * friar)310 static void finish_permission_event(struct fsnotify_group *group,
311 				    struct fanotify_perm_event *event, u32 response,
312 				    struct fanotify_response_info_audit_rule *friar)
313 				    __releases(&group->notification_lock)
314 {
315 	bool destroy = false;
316 
317 	assert_spin_locked(&group->notification_lock);
318 	event->response = response & ~FAN_INFO;
319 	if (response & FAN_INFO)
320 		memcpy(&event->audit_rule, friar, sizeof(*friar));
321 
322 	if (event->state == FAN_EVENT_CANCELED)
323 		destroy = true;
324 	else
325 		event->state = FAN_EVENT_ANSWERED;
326 	spin_unlock(&group->notification_lock);
327 	if (destroy)
328 		fsnotify_destroy_event(group, &event->fae.fse);
329 }
330 
process_access_response(struct fsnotify_group * group,struct fanotify_response * response_struct,const char __user * info,size_t info_len)331 static int process_access_response(struct fsnotify_group *group,
332 				   struct fanotify_response *response_struct,
333 				   const char __user *info,
334 				   size_t info_len)
335 {
336 	struct fanotify_perm_event *event;
337 	int fd = response_struct->fd;
338 	u32 response = response_struct->response;
339 	int ret = info_len;
340 	struct fanotify_response_info_audit_rule friar;
341 
342 	pr_debug("%s: group=%p fd=%d response=%u buf=%p size=%zu\n", __func__,
343 		 group, fd, response, info, info_len);
344 	/*
345 	 * make sure the response is valid, if invalid we do nothing and either
346 	 * userspace can send a valid response or we will clean it up after the
347 	 * timeout
348 	 */
349 	if (response & ~FANOTIFY_RESPONSE_VALID_MASK)
350 		return -EINVAL;
351 
352 	switch (response & FANOTIFY_RESPONSE_ACCESS) {
353 	case FAN_ALLOW:
354 	case FAN_DENY:
355 		break;
356 	default:
357 		return -EINVAL;
358 	}
359 
360 	if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
361 		return -EINVAL;
362 
363 	if (response & FAN_INFO) {
364 		ret = process_access_response_info(info, info_len, &friar);
365 		if (ret < 0)
366 			return ret;
367 		if (fd == FAN_NOFD)
368 			return ret;
369 	} else {
370 		ret = 0;
371 	}
372 
373 	if (fd < 0)
374 		return -EINVAL;
375 
376 	spin_lock(&group->notification_lock);
377 	list_for_each_entry(event, &group->fanotify_data.access_list,
378 			    fae.fse.list) {
379 		if (event->fd != fd)
380 			continue;
381 
382 		list_del_init(&event->fae.fse.list);
383 		finish_permission_event(group, event, response, &friar);
384 		wake_up(&group->fanotify_data.access_waitq);
385 		return ret;
386 	}
387 	spin_unlock(&group->notification_lock);
388 
389 	return -ENOENT;
390 }
391 
copy_error_info_to_user(struct fanotify_event * event,char __user * buf,int count)392 static size_t copy_error_info_to_user(struct fanotify_event *event,
393 				      char __user *buf, int count)
394 {
395 	struct fanotify_event_info_error info = { };
396 	struct fanotify_error_event *fee = FANOTIFY_EE(event);
397 
398 	info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
399 	info.hdr.len = FANOTIFY_ERROR_INFO_LEN;
400 
401 	if (WARN_ON(count < info.hdr.len))
402 		return -EFAULT;
403 
404 	info.error = fee->error;
405 	info.error_count = fee->err_count;
406 
407 	if (copy_to_user(buf, &info, sizeof(info)))
408 		return -EFAULT;
409 
410 	return info.hdr.len;
411 }
412 
copy_fid_info_to_user(__kernel_fsid_t * fsid,struct fanotify_fh * fh,int info_type,const char * name,size_t name_len,char __user * buf,size_t count)413 static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
414 				 int info_type, const char *name,
415 				 size_t name_len,
416 				 char __user *buf, size_t count)
417 {
418 	struct fanotify_event_info_fid info = { };
419 	struct file_handle handle = { };
420 	unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf;
421 	size_t fh_len = fh ? fh->len : 0;
422 	size_t info_len = fanotify_fid_info_len(fh_len, name_len);
423 	size_t len = info_len;
424 
425 	pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
426 		 __func__, fh_len, name_len, info_len, count);
427 
428 	if (WARN_ON_ONCE(len < sizeof(info) || len > count))
429 		return -EFAULT;
430 
431 	/*
432 	 * Copy event info fid header followed by variable sized file handle
433 	 * and optionally followed by variable sized filename.
434 	 */
435 	switch (info_type) {
436 	case FAN_EVENT_INFO_TYPE_FID:
437 	case FAN_EVENT_INFO_TYPE_DFID:
438 		if (WARN_ON_ONCE(name_len))
439 			return -EFAULT;
440 		break;
441 	case FAN_EVENT_INFO_TYPE_DFID_NAME:
442 	case FAN_EVENT_INFO_TYPE_OLD_DFID_NAME:
443 	case FAN_EVENT_INFO_TYPE_NEW_DFID_NAME:
444 		if (WARN_ON_ONCE(!name || !name_len))
445 			return -EFAULT;
446 		break;
447 	default:
448 		return -EFAULT;
449 	}
450 
451 	info.hdr.info_type = info_type;
452 	info.hdr.len = len;
453 	info.fsid = *fsid;
454 	if (copy_to_user(buf, &info, sizeof(info)))
455 		return -EFAULT;
456 
457 	buf += sizeof(info);
458 	len -= sizeof(info);
459 	if (WARN_ON_ONCE(len < sizeof(handle)))
460 		return -EFAULT;
461 
462 	handle.handle_type = fh->type;
463 	handle.handle_bytes = fh_len;
464 
465 	/* Mangle handle_type for bad file_handle */
466 	if (!fh_len)
467 		handle.handle_type = FILEID_INVALID;
468 
469 	if (copy_to_user(buf, &handle, sizeof(handle)))
470 		return -EFAULT;
471 
472 	buf += sizeof(handle);
473 	len -= sizeof(handle);
474 	if (WARN_ON_ONCE(len < fh_len))
475 		return -EFAULT;
476 
477 	/*
478 	 * For an inline fh and inline file name, copy through stack to exclude
479 	 * the copy from usercopy hardening protections.
480 	 */
481 	fh_buf = fanotify_fh_buf(fh);
482 	if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
483 		memcpy(bounce, fh_buf, fh_len);
484 		fh_buf = bounce;
485 	}
486 	if (copy_to_user(buf, fh_buf, fh_len))
487 		return -EFAULT;
488 
489 	buf += fh_len;
490 	len -= fh_len;
491 
492 	if (name_len) {
493 		/* Copy the filename with terminating null */
494 		name_len++;
495 		if (WARN_ON_ONCE(len < name_len))
496 			return -EFAULT;
497 
498 		if (copy_to_user(buf, name, name_len))
499 			return -EFAULT;
500 
501 		buf += name_len;
502 		len -= name_len;
503 	}
504 
505 	/* Pad with 0's */
506 	WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
507 	if (len > 0 && clear_user(buf, len))
508 		return -EFAULT;
509 
510 	return info_len;
511 }
512 
copy_pidfd_info_to_user(int pidfd,char __user * buf,size_t count)513 static int copy_pidfd_info_to_user(int pidfd,
514 				   char __user *buf,
515 				   size_t count)
516 {
517 	struct fanotify_event_info_pidfd info = { };
518 	size_t info_len = FANOTIFY_PIDFD_INFO_HDR_LEN;
519 
520 	if (WARN_ON_ONCE(info_len > count))
521 		return -EFAULT;
522 
523 	info.hdr.info_type = FAN_EVENT_INFO_TYPE_PIDFD;
524 	info.hdr.len = info_len;
525 	info.pidfd = pidfd;
526 
527 	if (copy_to_user(buf, &info, info_len))
528 		return -EFAULT;
529 
530 	return info_len;
531 }
532 
copy_info_records_to_user(struct fanotify_event * event,struct fanotify_info * info,unsigned int info_mode,int pidfd,char __user * buf,size_t count)533 static int copy_info_records_to_user(struct fanotify_event *event,
534 				     struct fanotify_info *info,
535 				     unsigned int info_mode, int pidfd,
536 				     char __user *buf, size_t count)
537 {
538 	int ret, total_bytes = 0, info_type = 0;
539 	unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;
540 	unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
541 
542 	/*
543 	 * Event info records order is as follows:
544 	 * 1. dir fid + name
545 	 * 2. (optional) new dir fid + new name
546 	 * 3. (optional) child fid
547 	 */
548 	if (fanotify_event_has_dir_fh(event)) {
549 		info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
550 					     FAN_EVENT_INFO_TYPE_DFID;
551 
552 		/* FAN_RENAME uses special info types */
553 		if (event->mask & FAN_RENAME)
554 			info_type = FAN_EVENT_INFO_TYPE_OLD_DFID_NAME;
555 
556 		ret = copy_fid_info_to_user(fanotify_event_fsid(event),
557 					    fanotify_info_dir_fh(info),
558 					    info_type,
559 					    fanotify_info_name(info),
560 					    info->name_len, buf, count);
561 		if (ret < 0)
562 			return ret;
563 
564 		buf += ret;
565 		count -= ret;
566 		total_bytes += ret;
567 	}
568 
569 	/* New dir fid+name may be reported in addition to old dir fid+name */
570 	if (fanotify_event_has_dir2_fh(event)) {
571 		info_type = FAN_EVENT_INFO_TYPE_NEW_DFID_NAME;
572 		ret = copy_fid_info_to_user(fanotify_event_fsid(event),
573 					    fanotify_info_dir2_fh(info),
574 					    info_type,
575 					    fanotify_info_name2(info),
576 					    info->name2_len, buf, count);
577 		if (ret < 0)
578 			return ret;
579 
580 		buf += ret;
581 		count -= ret;
582 		total_bytes += ret;
583 	}
584 
585 	if (fanotify_event_has_object_fh(event)) {
586 		const char *dot = NULL;
587 		int dot_len = 0;
588 
589 		if (fid_mode == FAN_REPORT_FID || info_type) {
590 			/*
591 			 * With only group flag FAN_REPORT_FID only type FID is
592 			 * reported. Second info record type is always FID.
593 			 */
594 			info_type = FAN_EVENT_INFO_TYPE_FID;
595 		} else if ((fid_mode & FAN_REPORT_NAME) &&
596 			   (event->mask & FAN_ONDIR)) {
597 			/*
598 			 * With group flag FAN_REPORT_NAME, if name was not
599 			 * recorded in an event on a directory, report the name
600 			 * "." with info type DFID_NAME.
601 			 */
602 			info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
603 			dot = ".";
604 			dot_len = 1;
605 		} else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
606 			   (event->mask & FAN_ONDIR)) {
607 			/*
608 			 * With group flag FAN_REPORT_DIR_FID, a single info
609 			 * record has type DFID for directory entry modification
610 			 * event and for event on a directory.
611 			 */
612 			info_type = FAN_EVENT_INFO_TYPE_DFID;
613 		} else {
614 			/*
615 			 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,
616 			 * a single info record has type FID for event on a
617 			 * non-directory, when there is no directory to report.
618 			 * For example, on FAN_DELETE_SELF event.
619 			 */
620 			info_type = FAN_EVENT_INFO_TYPE_FID;
621 		}
622 
623 		ret = copy_fid_info_to_user(fanotify_event_fsid(event),
624 					    fanotify_event_object_fh(event),
625 					    info_type, dot, dot_len,
626 					    buf, count);
627 		if (ret < 0)
628 			return ret;
629 
630 		buf += ret;
631 		count -= ret;
632 		total_bytes += ret;
633 	}
634 
635 	if (pidfd_mode) {
636 		ret = copy_pidfd_info_to_user(pidfd, buf, count);
637 		if (ret < 0)
638 			return ret;
639 
640 		buf += ret;
641 		count -= ret;
642 		total_bytes += ret;
643 	}
644 
645 	if (fanotify_is_error_event(event->mask)) {
646 		ret = copy_error_info_to_user(event, buf, count);
647 		if (ret < 0)
648 			return ret;
649 		buf += ret;
650 		count -= ret;
651 		total_bytes += ret;
652 	}
653 
654 	return total_bytes;
655 }
656 
copy_event_to_user(struct fsnotify_group * group,struct fanotify_event * event,char __user * buf,size_t count)657 static ssize_t copy_event_to_user(struct fsnotify_group *group,
658 				  struct fanotify_event *event,
659 				  char __user *buf, size_t count)
660 {
661 	struct fanotify_event_metadata metadata;
662 	const struct path *path = fanotify_event_path(event);
663 	struct fanotify_info *info = fanotify_event_info(event);
664 	unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
665 	unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
666 	struct file *f = NULL, *pidfd_file = NULL;
667 	int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD;
668 
669 	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
670 
671 	metadata.event_len = fanotify_event_len(info_mode, event);
672 	metadata.metadata_len = FAN_EVENT_METADATA_LEN;
673 	metadata.vers = FANOTIFY_METADATA_VERSION;
674 	metadata.reserved = 0;
675 	metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
676 	metadata.pid = pid_vnr(event->pid);
677 	/*
678 	 * For an unprivileged listener, event->pid can be used to identify the
679 	 * events generated by the listener process itself, without disclosing
680 	 * the pids of other processes.
681 	 */
682 	if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
683 	    task_tgid(current) != event->pid)
684 		metadata.pid = 0;
685 
686 	/*
687 	 * For now, fid mode is required for an unprivileged listener and
688 	 * fid mode does not report fd in events.  Keep this check anyway
689 	 * for safety in case fid mode requirement is relaxed in the future
690 	 * to allow unprivileged listener to get events with no fd and no fid.
691 	 */
692 	if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
693 	    path && path->mnt && path->dentry) {
694 		fd = create_fd(group, path, &f);
695 		if (fd < 0)
696 			return fd;
697 	}
698 	metadata.fd = fd;
699 
700 	if (pidfd_mode) {
701 		/*
702 		 * Complain if the FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
703 		 * exclusion is ever lifted. At the time of incoporating pidfd
704 		 * support within fanotify, the pidfd API only supported the
705 		 * creation of pidfds for thread-group leaders.
706 		 */
707 		WARN_ON_ONCE(FAN_GROUP_FLAG(group, FAN_REPORT_TID));
708 
709 		/*
710 		 * The PIDTYPE_TGID check for an event->pid is performed
711 		 * preemptively in an attempt to catch out cases where the event
712 		 * listener reads events after the event generating process has
713 		 * already terminated. Report FAN_NOPIDFD to the event listener
714 		 * in those cases, with all other pidfd creation errors being
715 		 * reported as FAN_EPIDFD.
716 		 */
717 		if (metadata.pid == 0 ||
718 		    !pid_has_task(event->pid, PIDTYPE_TGID)) {
719 			pidfd = FAN_NOPIDFD;
720 		} else {
721 			pidfd = pidfd_prepare(event->pid, 0, &pidfd_file);
722 			if (pidfd < 0)
723 				pidfd = FAN_EPIDFD;
724 		}
725 	}
726 
727 	ret = -EFAULT;
728 	/*
729 	 * Sanity check copy size in case get_one_event() and
730 	 * event_len sizes ever get out of sync.
731 	 */
732 	if (WARN_ON_ONCE(metadata.event_len > count))
733 		goto out_close_fd;
734 
735 	if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
736 		goto out_close_fd;
737 
738 	buf += FAN_EVENT_METADATA_LEN;
739 	count -= FAN_EVENT_METADATA_LEN;
740 
741 	if (fanotify_is_perm_event(event->mask))
742 		FANOTIFY_PERM(event)->fd = fd;
743 
744 	if (info_mode) {
745 		ret = copy_info_records_to_user(event, info, info_mode, pidfd,
746 						buf, count);
747 		if (ret < 0)
748 			goto out_close_fd;
749 	}
750 
751 	if (f)
752 		fd_install(fd, f);
753 
754 	if (pidfd_file)
755 		fd_install(pidfd, pidfd_file);
756 
757 	return metadata.event_len;
758 
759 out_close_fd:
760 	if (fd != FAN_NOFD) {
761 		put_unused_fd(fd);
762 		fput(f);
763 	}
764 
765 	if (pidfd >= 0) {
766 		put_unused_fd(pidfd);
767 		fput(pidfd_file);
768 	}
769 
770 	return ret;
771 }
772 
773 /* intofiy userspace file descriptor functions */
fanotify_poll(struct file * file,poll_table * wait)774 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
775 {
776 	struct fsnotify_group *group = file->private_data;
777 	__poll_t ret = 0;
778 
779 	poll_wait(file, &group->notification_waitq, wait);
780 	spin_lock(&group->notification_lock);
781 	if (!fsnotify_notify_queue_is_empty(group))
782 		ret = EPOLLIN | EPOLLRDNORM;
783 	spin_unlock(&group->notification_lock);
784 
785 	return ret;
786 }
787 
fanotify_read(struct file * file,char __user * buf,size_t count,loff_t * pos)788 static ssize_t fanotify_read(struct file *file, char __user *buf,
789 			     size_t count, loff_t *pos)
790 {
791 	struct fsnotify_group *group;
792 	struct fanotify_event *event;
793 	char __user *start;
794 	int ret;
795 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
796 
797 	start = buf;
798 	group = file->private_data;
799 
800 	pr_debug("%s: group=%p\n", __func__, group);
801 
802 	add_wait_queue(&group->notification_waitq, &wait);
803 	while (1) {
804 		/*
805 		 * User can supply arbitrarily large buffer. Avoid softlockups
806 		 * in case there are lots of available events.
807 		 */
808 		cond_resched();
809 		event = get_one_event(group, count);
810 		if (IS_ERR(event)) {
811 			ret = PTR_ERR(event);
812 			break;
813 		}
814 
815 		if (!event) {
816 			ret = -EAGAIN;
817 			if (file->f_flags & O_NONBLOCK)
818 				break;
819 
820 			ret = -ERESTARTSYS;
821 			if (signal_pending(current))
822 				break;
823 
824 			if (start != buf)
825 				break;
826 
827 			wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
828 			continue;
829 		}
830 
831 		ret = copy_event_to_user(group, event, buf, count);
832 		if (unlikely(ret == -EOPENSTALE)) {
833 			/*
834 			 * We cannot report events with stale fd so drop it.
835 			 * Setting ret to 0 will continue the event loop and
836 			 * do the right thing if there are no more events to
837 			 * read (i.e. return bytes read, -EAGAIN or wait).
838 			 */
839 			ret = 0;
840 		}
841 
842 		/*
843 		 * Permission events get queued to wait for response.  Other
844 		 * events can be destroyed now.
845 		 */
846 		if (!fanotify_is_perm_event(event->mask)) {
847 			fsnotify_destroy_event(group, &event->fse);
848 		} else {
849 			if (ret <= 0) {
850 				spin_lock(&group->notification_lock);
851 				finish_permission_event(group,
852 					FANOTIFY_PERM(event), FAN_DENY, NULL);
853 				wake_up(&group->fanotify_data.access_waitq);
854 			} else {
855 				spin_lock(&group->notification_lock);
856 				list_add_tail(&event->fse.list,
857 					&group->fanotify_data.access_list);
858 				spin_unlock(&group->notification_lock);
859 			}
860 		}
861 		if (ret < 0)
862 			break;
863 		buf += ret;
864 		count -= ret;
865 	}
866 	remove_wait_queue(&group->notification_waitq, &wait);
867 
868 	if (start != buf && ret != -EFAULT)
869 		ret = buf - start;
870 	return ret;
871 }
872 
fanotify_write(struct file * file,const char __user * buf,size_t count,loff_t * pos)873 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
874 {
875 	struct fanotify_response response;
876 	struct fsnotify_group *group;
877 	int ret;
878 	const char __user *info_buf = buf + sizeof(struct fanotify_response);
879 	size_t info_len;
880 
881 	if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
882 		return -EINVAL;
883 
884 	group = file->private_data;
885 
886 	pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
887 
888 	if (count < sizeof(response))
889 		return -EINVAL;
890 
891 	if (copy_from_user(&response, buf, sizeof(response)))
892 		return -EFAULT;
893 
894 	info_len = count - sizeof(response);
895 
896 	ret = process_access_response(group, &response, info_buf, info_len);
897 	if (ret < 0)
898 		count = ret;
899 	else
900 		count = sizeof(response) + ret;
901 
902 	return count;
903 }
904 
fanotify_release(struct inode * ignored,struct file * file)905 static int fanotify_release(struct inode *ignored, struct file *file)
906 {
907 	struct fsnotify_group *group = file->private_data;
908 	struct fsnotify_event *fsn_event;
909 
910 	/*
911 	 * Stop new events from arriving in the notification queue. since
912 	 * userspace cannot use fanotify fd anymore, no event can enter or
913 	 * leave access_list by now either.
914 	 */
915 	fsnotify_group_stop_queueing(group);
916 
917 	/*
918 	 * Process all permission events on access_list and notification queue
919 	 * and simulate reply from userspace.
920 	 */
921 	spin_lock(&group->notification_lock);
922 	while (!list_empty(&group->fanotify_data.access_list)) {
923 		struct fanotify_perm_event *event;
924 
925 		event = list_first_entry(&group->fanotify_data.access_list,
926 				struct fanotify_perm_event, fae.fse.list);
927 		list_del_init(&event->fae.fse.list);
928 		finish_permission_event(group, event, FAN_ALLOW, NULL);
929 		spin_lock(&group->notification_lock);
930 	}
931 
932 	/*
933 	 * Destroy all non-permission events. For permission events just
934 	 * dequeue them and set the response. They will be freed once the
935 	 * response is consumed and fanotify_get_response() returns.
936 	 */
937 	while ((fsn_event = fsnotify_remove_first_event(group))) {
938 		struct fanotify_event *event = FANOTIFY_E(fsn_event);
939 
940 		if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
941 			spin_unlock(&group->notification_lock);
942 			fsnotify_destroy_event(group, fsn_event);
943 		} else {
944 			finish_permission_event(group, FANOTIFY_PERM(event),
945 						FAN_ALLOW, NULL);
946 		}
947 		spin_lock(&group->notification_lock);
948 	}
949 	spin_unlock(&group->notification_lock);
950 
951 	/* Response for all permission events it set, wakeup waiters */
952 	wake_up(&group->fanotify_data.access_waitq);
953 
954 	/* matches the fanotify_init->fsnotify_alloc_group */
955 	fsnotify_destroy_group(group);
956 
957 	return 0;
958 }
959 
fanotify_ioctl(struct file * file,unsigned int cmd,unsigned long arg)960 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
961 {
962 	struct fsnotify_group *group;
963 	struct fsnotify_event *fsn_event;
964 	void __user *p;
965 	int ret = -ENOTTY;
966 	size_t send_len = 0;
967 
968 	group = file->private_data;
969 
970 	p = (void __user *) arg;
971 
972 	switch (cmd) {
973 	case FIONREAD:
974 		spin_lock(&group->notification_lock);
975 		list_for_each_entry(fsn_event, &group->notification_list, list)
976 			send_len += FAN_EVENT_METADATA_LEN;
977 		spin_unlock(&group->notification_lock);
978 		ret = put_user(send_len, (int __user *) p);
979 		break;
980 	}
981 
982 	return ret;
983 }
984 
985 static const struct file_operations fanotify_fops = {
986 	.show_fdinfo	= fanotify_show_fdinfo,
987 	.poll		= fanotify_poll,
988 	.read		= fanotify_read,
989 	.write		= fanotify_write,
990 	.fasync		= NULL,
991 	.release	= fanotify_release,
992 	.unlocked_ioctl	= fanotify_ioctl,
993 	.compat_ioctl	= compat_ptr_ioctl,
994 	.llseek		= noop_llseek,
995 };
996 
fanotify_find_path(int dfd,const char __user * filename,struct path * path,unsigned int flags,__u64 mask,unsigned int obj_type)997 static int fanotify_find_path(int dfd, const char __user *filename,
998 			      struct path *path, unsigned int flags, __u64 mask,
999 			      unsigned int obj_type)
1000 {
1001 	int ret;
1002 
1003 	pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
1004 		 dfd, filename, flags);
1005 
1006 	if (filename == NULL) {
1007 		struct fd f = fdget(dfd);
1008 
1009 		ret = -EBADF;
1010 		if (!f.file)
1011 			goto out;
1012 
1013 		ret = -ENOTDIR;
1014 		if ((flags & FAN_MARK_ONLYDIR) &&
1015 		    !(S_ISDIR(file_inode(f.file)->i_mode))) {
1016 			fdput(f);
1017 			goto out;
1018 		}
1019 
1020 		*path = f.file->f_path;
1021 		path_get(path);
1022 		fdput(f);
1023 	} else {
1024 		unsigned int lookup_flags = 0;
1025 
1026 		if (!(flags & FAN_MARK_DONT_FOLLOW))
1027 			lookup_flags |= LOOKUP_FOLLOW;
1028 		if (flags & FAN_MARK_ONLYDIR)
1029 			lookup_flags |= LOOKUP_DIRECTORY;
1030 
1031 		ret = user_path_at(dfd, filename, lookup_flags, path);
1032 		if (ret)
1033 			goto out;
1034 	}
1035 
1036 	/* you can only watch an inode if you have read permissions on it */
1037 	ret = path_permission(path, MAY_READ);
1038 	if (ret) {
1039 		path_put(path);
1040 		goto out;
1041 	}
1042 
1043 	ret = security_path_notify(path, mask, obj_type);
1044 	if (ret)
1045 		path_put(path);
1046 
1047 out:
1048 	return ret;
1049 }
1050 
fanotify_mark_remove_from_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int flags,__u32 umask,int * destroy)1051 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
1052 					    __u32 mask, unsigned int flags,
1053 					    __u32 umask, int *destroy)
1054 {
1055 	__u32 oldmask, newmask;
1056 
1057 	/* umask bits cannot be removed by user */
1058 	mask &= ~umask;
1059 	spin_lock(&fsn_mark->lock);
1060 	oldmask = fsnotify_calc_mask(fsn_mark);
1061 	if (!(flags & FANOTIFY_MARK_IGNORE_BITS)) {
1062 		fsn_mark->mask &= ~mask;
1063 	} else {
1064 		fsn_mark->ignore_mask &= ~mask;
1065 	}
1066 	newmask = fsnotify_calc_mask(fsn_mark);
1067 	/*
1068 	 * We need to keep the mark around even if remaining mask cannot
1069 	 * result in any events (e.g. mask == FAN_ONDIR) to support incremenal
1070 	 * changes to the mask.
1071 	 * Destroy mark when only umask bits remain.
1072 	 */
1073 	*destroy = !((fsn_mark->mask | fsn_mark->ignore_mask) & ~umask);
1074 	spin_unlock(&fsn_mark->lock);
1075 
1076 	return oldmask & ~newmask;
1077 }
1078 
fanotify_remove_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,__u32 mask,unsigned int flags,__u32 umask)1079 static int fanotify_remove_mark(struct fsnotify_group *group,
1080 				fsnotify_connp_t *connp, __u32 mask,
1081 				unsigned int flags, __u32 umask)
1082 {
1083 	struct fsnotify_mark *fsn_mark = NULL;
1084 	__u32 removed;
1085 	int destroy_mark;
1086 
1087 	fsnotify_group_lock(group);
1088 	fsn_mark = fsnotify_find_mark(connp, group);
1089 	if (!fsn_mark) {
1090 		fsnotify_group_unlock(group);
1091 		return -ENOENT;
1092 	}
1093 
1094 	removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
1095 						 umask, &destroy_mark);
1096 	if (removed & fsnotify_conn_mask(fsn_mark->connector))
1097 		fsnotify_recalc_mask(fsn_mark->connector);
1098 	if (destroy_mark)
1099 		fsnotify_detach_mark(fsn_mark);
1100 	fsnotify_group_unlock(group);
1101 	if (destroy_mark)
1102 		fsnotify_free_mark(fsn_mark);
1103 
1104 	/* matches the fsnotify_find_mark() */
1105 	fsnotify_put_mark(fsn_mark);
1106 	return 0;
1107 }
1108 
fanotify_remove_vfsmount_mark(struct fsnotify_group * group,struct vfsmount * mnt,__u32 mask,unsigned int flags,__u32 umask)1109 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
1110 					 struct vfsmount *mnt, __u32 mask,
1111 					 unsigned int flags, __u32 umask)
1112 {
1113 	return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
1114 				    mask, flags, umask);
1115 }
1116 
fanotify_remove_sb_mark(struct fsnotify_group * group,struct super_block * sb,__u32 mask,unsigned int flags,__u32 umask)1117 static int fanotify_remove_sb_mark(struct fsnotify_group *group,
1118 				   struct super_block *sb, __u32 mask,
1119 				   unsigned int flags, __u32 umask)
1120 {
1121 	return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask,
1122 				    flags, umask);
1123 }
1124 
fanotify_remove_inode_mark(struct fsnotify_group * group,struct inode * inode,__u32 mask,unsigned int flags,__u32 umask)1125 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
1126 				      struct inode *inode, __u32 mask,
1127 				      unsigned int flags, __u32 umask)
1128 {
1129 	return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask,
1130 				    flags, umask);
1131 }
1132 
fanotify_mark_update_flags(struct fsnotify_mark * fsn_mark,unsigned int fan_flags)1133 static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
1134 				       unsigned int fan_flags)
1135 {
1136 	bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);
1137 	unsigned int ignore = fan_flags & FANOTIFY_MARK_IGNORE_BITS;
1138 	bool recalc = false;
1139 
1140 	/*
1141 	 * When using FAN_MARK_IGNORE for the first time, mark starts using
1142 	 * independent event flags in ignore mask.  After that, trying to
1143 	 * update the ignore mask with the old FAN_MARK_IGNORED_MASK API
1144 	 * will result in EEXIST error.
1145 	 */
1146 	if (ignore == FAN_MARK_IGNORE)
1147 		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS;
1148 
1149 	/*
1150 	 * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to
1151 	 * the removal of the FS_MODIFY bit in calculated mask if it was set
1152 	 * because of an ignore mask that is now going to survive FS_MODIFY.
1153 	 */
1154 	if (ignore && (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1155 	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) {
1156 		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
1157 		if (!(fsn_mark->mask & FS_MODIFY))
1158 			recalc = true;
1159 	}
1160 
1161 	if (fsn_mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE ||
1162 	    want_iref == !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
1163 		return recalc;
1164 
1165 	/*
1166 	 * NO_IREF may be removed from a mark, but not added.
1167 	 * When removed, fsnotify_recalc_mask() will take the inode ref.
1168 	 */
1169 	WARN_ON_ONCE(!want_iref);
1170 	fsn_mark->flags &= ~FSNOTIFY_MARK_FLAG_NO_IREF;
1171 
1172 	return true;
1173 }
1174 
fanotify_mark_add_to_mask(struct fsnotify_mark * fsn_mark,__u32 mask,unsigned int fan_flags)1175 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
1176 				      __u32 mask, unsigned int fan_flags)
1177 {
1178 	bool recalc;
1179 
1180 	spin_lock(&fsn_mark->lock);
1181 	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
1182 		fsn_mark->mask |= mask;
1183 	else
1184 		fsn_mark->ignore_mask |= mask;
1185 
1186 	recalc = fsnotify_calc_mask(fsn_mark) &
1187 		~fsnotify_conn_mask(fsn_mark->connector);
1188 
1189 	recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
1190 	spin_unlock(&fsn_mark->lock);
1191 
1192 	return recalc;
1193 }
1194 
fanotify_add_new_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,unsigned int obj_type,unsigned int fan_flags,__kernel_fsid_t * fsid)1195 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
1196 						   fsnotify_connp_t *connp,
1197 						   unsigned int obj_type,
1198 						   unsigned int fan_flags,
1199 						   __kernel_fsid_t *fsid)
1200 {
1201 	struct ucounts *ucounts = group->fanotify_data.ucounts;
1202 	struct fsnotify_mark *mark;
1203 	int ret;
1204 
1205 	/*
1206 	 * Enforce per user marks limits per user in all containing user ns.
1207 	 * A group with FAN_UNLIMITED_MARKS does not contribute to mark count
1208 	 * in the limited groups account.
1209 	 */
1210 	if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS) &&
1211 	    !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
1212 		return ERR_PTR(-ENOSPC);
1213 
1214 	mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
1215 	if (!mark) {
1216 		ret = -ENOMEM;
1217 		goto out_dec_ucounts;
1218 	}
1219 
1220 	fsnotify_init_mark(mark, group);
1221 	if (fan_flags & FAN_MARK_EVICTABLE)
1222 		mark->flags |= FSNOTIFY_MARK_FLAG_NO_IREF;
1223 
1224 	ret = fsnotify_add_mark_locked(mark, connp, obj_type, 0, fsid);
1225 	if (ret) {
1226 		fsnotify_put_mark(mark);
1227 		goto out_dec_ucounts;
1228 	}
1229 
1230 	return mark;
1231 
1232 out_dec_ucounts:
1233 	if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS))
1234 		dec_ucount(ucounts, UCOUNT_FANOTIFY_MARKS);
1235 	return ERR_PTR(ret);
1236 }
1237 
fanotify_group_init_error_pool(struct fsnotify_group * group)1238 static int fanotify_group_init_error_pool(struct fsnotify_group *group)
1239 {
1240 	if (mempool_initialized(&group->fanotify_data.error_events_pool))
1241 		return 0;
1242 
1243 	return mempool_init_kmalloc_pool(&group->fanotify_data.error_events_pool,
1244 					 FANOTIFY_DEFAULT_FEE_POOL_SIZE,
1245 					 sizeof(struct fanotify_error_event));
1246 }
1247 
fanotify_may_update_existing_mark(struct fsnotify_mark * fsn_mark,unsigned int fan_flags)1248 static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark,
1249 					      unsigned int fan_flags)
1250 {
1251 	/*
1252 	 * Non evictable mark cannot be downgraded to evictable mark.
1253 	 */
1254 	if (fan_flags & FAN_MARK_EVICTABLE &&
1255 	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
1256 		return -EEXIST;
1257 
1258 	/*
1259 	 * New ignore mask semantics cannot be downgraded to old semantics.
1260 	 */
1261 	if (fan_flags & FAN_MARK_IGNORED_MASK &&
1262 	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
1263 		return -EEXIST;
1264 
1265 	/*
1266 	 * An ignore mask that survives modify could never be downgraded to not
1267 	 * survive modify.  With new FAN_MARK_IGNORE semantics we make that rule
1268 	 * explicit and return an error when trying to update the ignore mask
1269 	 * without the original FAN_MARK_IGNORED_SURV_MODIFY value.
1270 	 */
1271 	if (fan_flags & FAN_MARK_IGNORE &&
1272 	    !(fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1273 	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
1274 		return -EEXIST;
1275 
1276 	return 0;
1277 }
1278 
fanotify_add_mark(struct fsnotify_group * group,fsnotify_connp_t * connp,unsigned int obj_type,__u32 mask,unsigned int fan_flags,__kernel_fsid_t * fsid)1279 static int fanotify_add_mark(struct fsnotify_group *group,
1280 			     fsnotify_connp_t *connp, unsigned int obj_type,
1281 			     __u32 mask, unsigned int fan_flags,
1282 			     __kernel_fsid_t *fsid)
1283 {
1284 	struct fsnotify_mark *fsn_mark;
1285 	bool recalc;
1286 	int ret = 0;
1287 
1288 	fsnotify_group_lock(group);
1289 	fsn_mark = fsnotify_find_mark(connp, group);
1290 	if (!fsn_mark) {
1291 		fsn_mark = fanotify_add_new_mark(group, connp, obj_type,
1292 						 fan_flags, fsid);
1293 		if (IS_ERR(fsn_mark)) {
1294 			fsnotify_group_unlock(group);
1295 			return PTR_ERR(fsn_mark);
1296 		}
1297 	}
1298 
1299 	/*
1300 	 * Check if requested mark flags conflict with an existing mark flags.
1301 	 */
1302 	ret = fanotify_may_update_existing_mark(fsn_mark, fan_flags);
1303 	if (ret)
1304 		goto out;
1305 
1306 	/*
1307 	 * Error events are pre-allocated per group, only if strictly
1308 	 * needed (i.e. FAN_FS_ERROR was requested).
1309 	 */
1310 	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS) &&
1311 	    (mask & FAN_FS_ERROR)) {
1312 		ret = fanotify_group_init_error_pool(group);
1313 		if (ret)
1314 			goto out;
1315 	}
1316 
1317 	recalc = fanotify_mark_add_to_mask(fsn_mark, mask, fan_flags);
1318 	if (recalc)
1319 		fsnotify_recalc_mask(fsn_mark->connector);
1320 
1321 out:
1322 	fsnotify_group_unlock(group);
1323 
1324 	fsnotify_put_mark(fsn_mark);
1325 	return ret;
1326 }
1327 
fanotify_add_vfsmount_mark(struct fsnotify_group * group,struct vfsmount * mnt,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1328 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
1329 				      struct vfsmount *mnt, __u32 mask,
1330 				      unsigned int flags, __kernel_fsid_t *fsid)
1331 {
1332 	return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
1333 				 FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid);
1334 }
1335 
fanotify_add_sb_mark(struct fsnotify_group * group,struct super_block * sb,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1336 static int fanotify_add_sb_mark(struct fsnotify_group *group,
1337 				struct super_block *sb, __u32 mask,
1338 				unsigned int flags, __kernel_fsid_t *fsid)
1339 {
1340 	return fanotify_add_mark(group, &sb->s_fsnotify_marks,
1341 				 FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid);
1342 }
1343 
fanotify_add_inode_mark(struct fsnotify_group * group,struct inode * inode,__u32 mask,unsigned int flags,__kernel_fsid_t * fsid)1344 static int fanotify_add_inode_mark(struct fsnotify_group *group,
1345 				   struct inode *inode, __u32 mask,
1346 				   unsigned int flags, __kernel_fsid_t *fsid)
1347 {
1348 	pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
1349 
1350 	/*
1351 	 * If some other task has this inode open for write we should not add
1352 	 * an ignore mask, unless that ignore mask is supposed to survive
1353 	 * modification changes anyway.
1354 	 */
1355 	if ((flags & FANOTIFY_MARK_IGNORE_BITS) &&
1356 	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
1357 	    inode_is_open_for_write(inode))
1358 		return 0;
1359 
1360 	return fanotify_add_mark(group, &inode->i_fsnotify_marks,
1361 				 FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
1362 }
1363 
fanotify_alloc_overflow_event(void)1364 static struct fsnotify_event *fanotify_alloc_overflow_event(void)
1365 {
1366 	struct fanotify_event *oevent;
1367 
1368 	oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
1369 	if (!oevent)
1370 		return NULL;
1371 
1372 	fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
1373 	oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
1374 
1375 	return &oevent->fse;
1376 }
1377 
fanotify_alloc_merge_hash(void)1378 static struct hlist_head *fanotify_alloc_merge_hash(void)
1379 {
1380 	struct hlist_head *hash;
1381 
1382 	hash = kmalloc(sizeof(struct hlist_head) << FANOTIFY_HTABLE_BITS,
1383 		       GFP_KERNEL_ACCOUNT);
1384 	if (!hash)
1385 		return NULL;
1386 
1387 	__hash_init(hash, FANOTIFY_HTABLE_SIZE);
1388 
1389 	return hash;
1390 }
1391 
1392 /* fanotify syscalls */
SYSCALL_DEFINE2(fanotify_init,unsigned int,flags,unsigned int,event_f_flags)1393 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
1394 {
1395 	struct fsnotify_group *group;
1396 	int f_flags, fd;
1397 	unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
1398 	unsigned int class = flags & FANOTIFY_CLASS_BITS;
1399 	unsigned int internal_flags = 0;
1400 
1401 	pr_debug("%s: flags=%x event_f_flags=%x\n",
1402 		 __func__, flags, event_f_flags);
1403 
1404 	if (!capable(CAP_SYS_ADMIN)) {
1405 		/*
1406 		 * An unprivileged user can setup an fanotify group with
1407 		 * limited functionality - an unprivileged group is limited to
1408 		 * notification events with file handles and it cannot use
1409 		 * unlimited queue/marks.
1410 		 */
1411 		if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) || !fid_mode)
1412 			return -EPERM;
1413 
1414 		/*
1415 		 * Setting the internal flag FANOTIFY_UNPRIV on the group
1416 		 * prevents setting mount/filesystem marks on this group and
1417 		 * prevents reporting pid and open fd in events.
1418 		 */
1419 		internal_flags |= FANOTIFY_UNPRIV;
1420 	}
1421 
1422 #ifdef CONFIG_AUDITSYSCALL
1423 	if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
1424 #else
1425 	if (flags & ~FANOTIFY_INIT_FLAGS)
1426 #endif
1427 		return -EINVAL;
1428 
1429 	/*
1430 	 * A pidfd can only be returned for a thread-group leader; thus
1431 	 * FAN_REPORT_PIDFD and FAN_REPORT_TID need to remain mutually
1432 	 * exclusive.
1433 	 */
1434 	if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
1435 		return -EINVAL;
1436 
1437 	if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
1438 		return -EINVAL;
1439 
1440 	switch (event_f_flags & O_ACCMODE) {
1441 	case O_RDONLY:
1442 	case O_RDWR:
1443 	case O_WRONLY:
1444 		break;
1445 	default:
1446 		return -EINVAL;
1447 	}
1448 
1449 	if (fid_mode && class != FAN_CLASS_NOTIF)
1450 		return -EINVAL;
1451 
1452 	/*
1453 	 * Child name is reported with parent fid so requires dir fid.
1454 	 * We can report both child fid and dir fid with or without name.
1455 	 */
1456 	if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
1457 		return -EINVAL;
1458 
1459 	/*
1460 	 * FAN_REPORT_TARGET_FID requires FAN_REPORT_NAME and FAN_REPORT_FID
1461 	 * and is used as an indication to report both dir and child fid on all
1462 	 * dirent events.
1463 	 */
1464 	if ((fid_mode & FAN_REPORT_TARGET_FID) &&
1465 	    (!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
1466 		return -EINVAL;
1467 
1468 	f_flags = O_RDWR | __FMODE_NONOTIFY;
1469 	if (flags & FAN_CLOEXEC)
1470 		f_flags |= O_CLOEXEC;
1471 	if (flags & FAN_NONBLOCK)
1472 		f_flags |= O_NONBLOCK;
1473 
1474 	/* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
1475 	group = fsnotify_alloc_group(&fanotify_fsnotify_ops,
1476 				     FSNOTIFY_GROUP_USER | FSNOTIFY_GROUP_NOFS);
1477 	if (IS_ERR(group)) {
1478 		return PTR_ERR(group);
1479 	}
1480 
1481 	/* Enforce groups limits per user in all containing user ns */
1482 	group->fanotify_data.ucounts = inc_ucount(current_user_ns(),
1483 						  current_euid(),
1484 						  UCOUNT_FANOTIFY_GROUPS);
1485 	if (!group->fanotify_data.ucounts) {
1486 		fd = -EMFILE;
1487 		goto out_destroy_group;
1488 	}
1489 
1490 	group->fanotify_data.flags = flags | internal_flags;
1491 	group->memcg = get_mem_cgroup_from_mm(current->mm);
1492 
1493 	group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
1494 	if (!group->fanotify_data.merge_hash) {
1495 		fd = -ENOMEM;
1496 		goto out_destroy_group;
1497 	}
1498 
1499 	group->overflow_event = fanotify_alloc_overflow_event();
1500 	if (unlikely(!group->overflow_event)) {
1501 		fd = -ENOMEM;
1502 		goto out_destroy_group;
1503 	}
1504 
1505 	if (force_o_largefile())
1506 		event_f_flags |= O_LARGEFILE;
1507 	group->fanotify_data.f_flags = event_f_flags;
1508 	init_waitqueue_head(&group->fanotify_data.access_waitq);
1509 	INIT_LIST_HEAD(&group->fanotify_data.access_list);
1510 	switch (class) {
1511 	case FAN_CLASS_NOTIF:
1512 		group->priority = FS_PRIO_0;
1513 		break;
1514 	case FAN_CLASS_CONTENT:
1515 		group->priority = FS_PRIO_1;
1516 		break;
1517 	case FAN_CLASS_PRE_CONTENT:
1518 		group->priority = FS_PRIO_2;
1519 		break;
1520 	default:
1521 		fd = -EINVAL;
1522 		goto out_destroy_group;
1523 	}
1524 
1525 	if (flags & FAN_UNLIMITED_QUEUE) {
1526 		fd = -EPERM;
1527 		if (!capable(CAP_SYS_ADMIN))
1528 			goto out_destroy_group;
1529 		group->max_events = UINT_MAX;
1530 	} else {
1531 		group->max_events = fanotify_max_queued_events;
1532 	}
1533 
1534 	if (flags & FAN_UNLIMITED_MARKS) {
1535 		fd = -EPERM;
1536 		if (!capable(CAP_SYS_ADMIN))
1537 			goto out_destroy_group;
1538 	}
1539 
1540 	if (flags & FAN_ENABLE_AUDIT) {
1541 		fd = -EPERM;
1542 		if (!capable(CAP_AUDIT_WRITE))
1543 			goto out_destroy_group;
1544 	}
1545 
1546 	fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
1547 	if (fd < 0)
1548 		goto out_destroy_group;
1549 
1550 	return fd;
1551 
1552 out_destroy_group:
1553 	fsnotify_destroy_group(group);
1554 	return fd;
1555 }
1556 
fanotify_test_fsid(struct dentry * dentry,__kernel_fsid_t * fsid)1557 static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
1558 {
1559 	__kernel_fsid_t root_fsid;
1560 	int err;
1561 
1562 	/*
1563 	 * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
1564 	 */
1565 	err = vfs_get_fsid(dentry, fsid);
1566 	if (err)
1567 		return err;
1568 
1569 	if (!fsid->val[0] && !fsid->val[1])
1570 		return -ENODEV;
1571 
1572 	/*
1573 	 * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
1574 	 * which uses a different fsid than sb root.
1575 	 */
1576 	err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
1577 	if (err)
1578 		return err;
1579 
1580 	if (root_fsid.val[0] != fsid->val[0] ||
1581 	    root_fsid.val[1] != fsid->val[1])
1582 		return -EXDEV;
1583 
1584 	return 0;
1585 }
1586 
1587 /* Check if filesystem can encode a unique fid */
fanotify_test_fid(struct dentry * dentry,unsigned int flags)1588 static int fanotify_test_fid(struct dentry *dentry, unsigned int flags)
1589 {
1590 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1591 	const struct export_operations *nop = dentry->d_sb->s_export_op;
1592 
1593 	/*
1594 	 * We need to make sure that the filesystem supports encoding of
1595 	 * file handles so user can use name_to_handle_at() to compare fids
1596 	 * reported with events to the file handle of watched objects.
1597 	 */
1598 	if (!nop)
1599 		return -EOPNOTSUPP;
1600 
1601 	/*
1602 	 * For sb/mount mark, we also need to make sure that the filesystem
1603 	 * supports decoding file handles, so user has a way to map back the
1604 	 * reported fids to filesystem objects.
1605 	 */
1606 	if (mark_type != FAN_MARK_INODE && !nop->fh_to_dentry)
1607 		return -EOPNOTSUPP;
1608 
1609 	return 0;
1610 }
1611 
fanotify_events_supported(struct fsnotify_group * group,const struct path * path,__u64 mask,unsigned int flags)1612 static int fanotify_events_supported(struct fsnotify_group *group,
1613 				     const struct path *path, __u64 mask,
1614 				     unsigned int flags)
1615 {
1616 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1617 	/* Strict validation of events in non-dir inode mask with v5.17+ APIs */
1618 	bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
1619 				 (mask & FAN_RENAME) ||
1620 				 (flags & FAN_MARK_IGNORE);
1621 
1622 	/*
1623 	 * Some filesystems such as 'proc' acquire unusual locks when opening
1624 	 * files. For them fanotify permission events have high chances of
1625 	 * deadlocking the system - open done when reporting fanotify event
1626 	 * blocks on this "unusual" lock while another process holding the lock
1627 	 * waits for fanotify permission event to be answered. Just disallow
1628 	 * permission events for such filesystems.
1629 	 */
1630 	if (mask & FANOTIFY_PERM_EVENTS &&
1631 	    path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
1632 		return -EINVAL;
1633 
1634 	/*
1635 	 * mount and sb marks are not allowed on kernel internal pseudo fs,
1636 	 * like pipe_mnt, because that would subscribe to events on all the
1637 	 * anonynous pipes in the system.
1638 	 *
1639 	 * SB_NOUSER covers all of the internal pseudo fs whose objects are not
1640 	 * exposed to user's mount namespace, but there are other SB_KERNMOUNT
1641 	 * fs, like nsfs, debugfs, for which the value of allowing sb and mount
1642 	 * mark is questionable. For now we leave them alone.
1643 	 */
1644 	if (mark_type != FAN_MARK_INODE &&
1645 	    path->mnt->mnt_sb->s_flags & SB_NOUSER)
1646 		return -EINVAL;
1647 
1648 	/*
1649 	 * We shouldn't have allowed setting dirent events and the directory
1650 	 * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,
1651 	 * but because we always allowed it, error only when using new APIs.
1652 	 */
1653 	if (strict_dir_events && mark_type == FAN_MARK_INODE &&
1654 	    !d_is_dir(path->dentry) && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
1655 		return -ENOTDIR;
1656 
1657 	return 0;
1658 }
1659 
do_fanotify_mark(int fanotify_fd,unsigned int flags,__u64 mask,int dfd,const char __user * pathname)1660 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
1661 			    int dfd, const char  __user *pathname)
1662 {
1663 	struct inode *inode = NULL;
1664 	struct vfsmount *mnt = NULL;
1665 	struct fsnotify_group *group;
1666 	struct fd f;
1667 	struct path path;
1668 	__kernel_fsid_t __fsid, *fsid = NULL;
1669 	u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
1670 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
1671 	unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;
1672 	unsigned int ignore = flags & FANOTIFY_MARK_IGNORE_BITS;
1673 	unsigned int obj_type, fid_mode;
1674 	u32 umask = 0;
1675 	int ret;
1676 
1677 	pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
1678 		 __func__, fanotify_fd, flags, dfd, pathname, mask);
1679 
1680 	/* we only use the lower 32 bits as of right now. */
1681 	if (upper_32_bits(mask))
1682 		return -EINVAL;
1683 
1684 	if (flags & ~FANOTIFY_MARK_FLAGS)
1685 		return -EINVAL;
1686 
1687 	switch (mark_type) {
1688 	case FAN_MARK_INODE:
1689 		obj_type = FSNOTIFY_OBJ_TYPE_INODE;
1690 		break;
1691 	case FAN_MARK_MOUNT:
1692 		obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
1693 		break;
1694 	case FAN_MARK_FILESYSTEM:
1695 		obj_type = FSNOTIFY_OBJ_TYPE_SB;
1696 		break;
1697 	default:
1698 		return -EINVAL;
1699 	}
1700 
1701 	switch (mark_cmd) {
1702 	case FAN_MARK_ADD:
1703 	case FAN_MARK_REMOVE:
1704 		if (!mask)
1705 			return -EINVAL;
1706 		break;
1707 	case FAN_MARK_FLUSH:
1708 		if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
1709 			return -EINVAL;
1710 		break;
1711 	default:
1712 		return -EINVAL;
1713 	}
1714 
1715 	if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
1716 		valid_mask |= FANOTIFY_PERM_EVENTS;
1717 
1718 	if (mask & ~valid_mask)
1719 		return -EINVAL;
1720 
1721 
1722 	/* We don't allow FAN_MARK_IGNORE & FAN_MARK_IGNORED_MASK together */
1723 	if (ignore == (FAN_MARK_IGNORE | FAN_MARK_IGNORED_MASK))
1724 		return -EINVAL;
1725 
1726 	/*
1727 	 * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with
1728 	 * FAN_MARK_IGNORED_MASK.
1729 	 */
1730 	if (ignore == FAN_MARK_IGNORED_MASK) {
1731 		mask &= ~FANOTIFY_EVENT_FLAGS;
1732 		umask = FANOTIFY_EVENT_FLAGS;
1733 	}
1734 
1735 	f = fdget(fanotify_fd);
1736 	if (unlikely(!f.file))
1737 		return -EBADF;
1738 
1739 	/* verify that this is indeed an fanotify instance */
1740 	ret = -EINVAL;
1741 	if (unlikely(f.file->f_op != &fanotify_fops))
1742 		goto fput_and_out;
1743 	group = f.file->private_data;
1744 
1745 	/*
1746 	 * An unprivileged user is not allowed to setup mount nor filesystem
1747 	 * marks.  This also includes setting up such marks by a group that
1748 	 * was initialized by an unprivileged user.
1749 	 */
1750 	ret = -EPERM;
1751 	if ((!capable(CAP_SYS_ADMIN) ||
1752 	     FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV)) &&
1753 	    mark_type != FAN_MARK_INODE)
1754 		goto fput_and_out;
1755 
1756 	/*
1757 	 * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
1758 	 * allowed to set permissions events.
1759 	 */
1760 	ret = -EINVAL;
1761 	if (mask & FANOTIFY_PERM_EVENTS &&
1762 	    group->priority == FS_PRIO_0)
1763 		goto fput_and_out;
1764 
1765 	if (mask & FAN_FS_ERROR &&
1766 	    mark_type != FAN_MARK_FILESYSTEM)
1767 		goto fput_and_out;
1768 
1769 	/*
1770 	 * Evictable is only relevant for inode marks, because only inode object
1771 	 * can be evicted on memory pressure.
1772 	 */
1773 	if (flags & FAN_MARK_EVICTABLE &&
1774 	     mark_type != FAN_MARK_INODE)
1775 		goto fput_and_out;
1776 
1777 	/*
1778 	 * Events that do not carry enough information to report
1779 	 * event->fd require a group that supports reporting fid.  Those
1780 	 * events are not supported on a mount mark, because they do not
1781 	 * carry enough information (i.e. path) to be filtered by mount
1782 	 * point.
1783 	 */
1784 	fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
1785 	if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_EVENT_FLAGS) &&
1786 	    (!fid_mode || mark_type == FAN_MARK_MOUNT))
1787 		goto fput_and_out;
1788 
1789 	/*
1790 	 * FAN_RENAME uses special info type records to report the old and
1791 	 * new parent+name.  Reporting only old and new parent id is less
1792 	 * useful and was not implemented.
1793 	 */
1794 	if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
1795 		goto fput_and_out;
1796 
1797 	if (mark_cmd == FAN_MARK_FLUSH) {
1798 		ret = 0;
1799 		if (mark_type == FAN_MARK_MOUNT)
1800 			fsnotify_clear_vfsmount_marks_by_group(group);
1801 		else if (mark_type == FAN_MARK_FILESYSTEM)
1802 			fsnotify_clear_sb_marks_by_group(group);
1803 		else
1804 			fsnotify_clear_inode_marks_by_group(group);
1805 		goto fput_and_out;
1806 	}
1807 
1808 	ret = fanotify_find_path(dfd, pathname, &path, flags,
1809 			(mask & ALL_FSNOTIFY_EVENTS), obj_type);
1810 	if (ret)
1811 		goto fput_and_out;
1812 
1813 	if (mark_cmd == FAN_MARK_ADD) {
1814 		ret = fanotify_events_supported(group, &path, mask, flags);
1815 		if (ret)
1816 			goto path_put_and_out;
1817 	}
1818 
1819 	if (fid_mode) {
1820 		ret = fanotify_test_fsid(path.dentry, &__fsid);
1821 		if (ret)
1822 			goto path_put_and_out;
1823 
1824 		ret = fanotify_test_fid(path.dentry, flags);
1825 		if (ret)
1826 			goto path_put_and_out;
1827 
1828 		fsid = &__fsid;
1829 	}
1830 
1831 	/* inode held in place by reference to path; group by fget on fd */
1832 	if (mark_type == FAN_MARK_INODE)
1833 		inode = path.dentry->d_inode;
1834 	else
1835 		mnt = path.mnt;
1836 
1837 	ret = mnt ? -EINVAL : -EISDIR;
1838 	/* FAN_MARK_IGNORE requires SURV_MODIFY for sb/mount/dir marks */
1839 	if (mark_cmd == FAN_MARK_ADD && ignore == FAN_MARK_IGNORE &&
1840 	    (mnt || S_ISDIR(inode->i_mode)) &&
1841 	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY))
1842 		goto path_put_and_out;
1843 
1844 	/* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
1845 	if (mnt || !S_ISDIR(inode->i_mode)) {
1846 		mask &= ~FAN_EVENT_ON_CHILD;
1847 		umask = FAN_EVENT_ON_CHILD;
1848 		/*
1849 		 * If group needs to report parent fid, register for getting
1850 		 * events with parent/name info for non-directory.
1851 		 */
1852 		if ((fid_mode & FAN_REPORT_DIR_FID) &&
1853 		    (flags & FAN_MARK_ADD) && !ignore)
1854 			mask |= FAN_EVENT_ON_CHILD;
1855 	}
1856 
1857 	/* create/update an inode mark */
1858 	switch (mark_cmd) {
1859 	case FAN_MARK_ADD:
1860 		if (mark_type == FAN_MARK_MOUNT)
1861 			ret = fanotify_add_vfsmount_mark(group, mnt, mask,
1862 							 flags, fsid);
1863 		else if (mark_type == FAN_MARK_FILESYSTEM)
1864 			ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
1865 						   flags, fsid);
1866 		else
1867 			ret = fanotify_add_inode_mark(group, inode, mask,
1868 						      flags, fsid);
1869 		break;
1870 	case FAN_MARK_REMOVE:
1871 		if (mark_type == FAN_MARK_MOUNT)
1872 			ret = fanotify_remove_vfsmount_mark(group, mnt, mask,
1873 							    flags, umask);
1874 		else if (mark_type == FAN_MARK_FILESYSTEM)
1875 			ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask,
1876 						      flags, umask);
1877 		else
1878 			ret = fanotify_remove_inode_mark(group, inode, mask,
1879 							 flags, umask);
1880 		break;
1881 	default:
1882 		ret = -EINVAL;
1883 	}
1884 
1885 path_put_and_out:
1886 	path_put(&path);
1887 fput_and_out:
1888 	fdput(f);
1889 	return ret;
1890 }
1891 
1892 #ifndef CONFIG_ARCH_SPLIT_ARG64
SYSCALL_DEFINE5(fanotify_mark,int,fanotify_fd,unsigned int,flags,__u64,mask,int,dfd,const char __user *,pathname)1893 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
1894 			      __u64, mask, int, dfd,
1895 			      const char  __user *, pathname)
1896 {
1897 	return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
1898 }
1899 #endif
1900 
1901 #if defined(CONFIG_ARCH_SPLIT_ARG64) || defined(CONFIG_COMPAT)
SYSCALL32_DEFINE6(fanotify_mark,int,fanotify_fd,unsigned int,flags,SC_ARG64 (mask),int,dfd,const char __user *,pathname)1902 SYSCALL32_DEFINE6(fanotify_mark,
1903 				int, fanotify_fd, unsigned int, flags,
1904 				SC_ARG64(mask), int, dfd,
1905 				const char  __user *, pathname)
1906 {
1907 	return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask),
1908 				dfd, pathname);
1909 }
1910 #endif
1911 
1912 /*
1913  * fanotify_user_setup - Our initialization function.  Note that we cannot return
1914  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
1915  * must result in panic().
1916  */
fanotify_user_setup(void)1917 static int __init fanotify_user_setup(void)
1918 {
1919 	struct sysinfo si;
1920 	int max_marks;
1921 
1922 	si_meminfo(&si);
1923 	/*
1924 	 * Allow up to 1% of addressable memory to be accounted for per user
1925 	 * marks limited to the range [8192, 1048576]. mount and sb marks are
1926 	 * a lot cheaper than inode marks, but there is no reason for a user
1927 	 * to have many of those, so calculate by the cost of inode marks.
1928 	 */
1929 	max_marks = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) /
1930 		    INODE_MARK_COST;
1931 	max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
1932 				     FANOTIFY_DEFAULT_MAX_USER_MARKS);
1933 
1934 	BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
1935 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 12);
1936 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);
1937 
1938 	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
1939 					 SLAB_PANIC|SLAB_ACCOUNT);
1940 	fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
1941 					       SLAB_PANIC);
1942 	fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
1943 						SLAB_PANIC);
1944 	if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
1945 		fanotify_perm_event_cachep =
1946 			KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
1947 	}
1948 
1949 	fanotify_max_queued_events = FANOTIFY_DEFAULT_MAX_EVENTS;
1950 	init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS] =
1951 					FANOTIFY_DEFAULT_MAX_GROUPS;
1952 	init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS] = max_marks;
1953 	fanotify_sysctls_init();
1954 
1955 	return 0;
1956 }
1957 device_initcall(fanotify_user_setup);
1958