1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * Filesystem access notification for Linux
4  *
5  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
6  */
7 
8 #ifndef __LINUX_FSNOTIFY_BACKEND_H
9 #define __LINUX_FSNOTIFY_BACKEND_H
10 
11 #ifdef __KERNEL__
12 
13 #include <linux/idr.h> /* inotify uses this */
14 #include <linux/fs.h> /* struct inode */
15 #include <linux/list.h>
16 #include <linux/path.h> /* struct path */
17 #include <linux/spinlock.h>
18 #include <linux/types.h>
19 #include <linux/atomic.h>
20 #include <linux/user_namespace.h>
21 #include <linux/refcount.h>
22 #include <linux/mempool.h>
23 #include <linux/sched/mm.h>
24 
25 /*
26  * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
27  * convert between them.  dnotify only needs conversion at watch creation
28  * so no perf loss there.  fanotify isn't defined yet, so it can use the
29  * wholes if it needs more events.
30  */
31 #define FS_ACCESS		0x00000001	/* File was accessed */
32 #define FS_MODIFY		0x00000002	/* File was modified */
33 #define FS_ATTRIB		0x00000004	/* Metadata changed */
34 #define FS_CLOSE_WRITE		0x00000008	/* Writtable file was closed */
35 #define FS_CLOSE_NOWRITE	0x00000010	/* Unwrittable file closed */
36 #define FS_OPEN			0x00000020	/* File was opened */
37 #define FS_MOVED_FROM		0x00000040	/* File was moved from X */
38 #define FS_MOVED_TO		0x00000080	/* File was moved to Y */
39 #define FS_CREATE		0x00000100	/* Subfile was created */
40 #define FS_DELETE		0x00000200	/* Subfile was deleted */
41 #define FS_DELETE_SELF		0x00000400	/* Self was deleted */
42 #define FS_MOVE_SELF		0x00000800	/* Self was moved */
43 #define FS_OPEN_EXEC		0x00001000	/* File was opened for exec */
44 
45 #define FS_UNMOUNT		0x00002000	/* inode on umount fs */
46 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
47 #define FS_ERROR		0x00008000	/* Filesystem Error (fanotify) */
48 
49 /*
50  * FS_IN_IGNORED overloads FS_ERROR.  It is only used internally by inotify
51  * which does not support FS_ERROR.
52  */
53 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
54 
55 #define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
56 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
57 #define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec event in a permission hook */
58 
59 /*
60  * Set on inode mark that cares about things that happen to its children.
61  * Always set for dnotify and inotify.
62  * Set on inode/sb/mount marks that care about parent/name info.
63  */
64 #define FS_EVENT_ON_CHILD	0x08000000
65 
66 #define FS_RENAME		0x10000000	/* File was renamed */
67 #define FS_DN_MULTISHOT		0x20000000	/* dnotify multishot */
68 #define FS_ISDIR		0x40000000	/* event occurred against dir */
69 
70 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)
71 
72 /*
73  * Directory entry modification events - reported only to directory
74  * where entry is modified and not to a watching parent.
75  * The watching parent may get an FS_ATTRIB|FS_EVENT_ON_CHILD event
76  * when a directory entry inside a child subdir changes.
77  */
78 #define ALL_FSNOTIFY_DIRENT_EVENTS (FS_CREATE | FS_DELETE | FS_MOVE | FS_RENAME)
79 
80 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \
81 				  FS_OPEN_EXEC_PERM)
82 
83 /*
84  * This is a list of all events that may get sent to a parent that is watching
85  * with flag FS_EVENT_ON_CHILD based on fs event on a child of that directory.
86  */
87 #define FS_EVENTS_POSS_ON_CHILD   (ALL_FSNOTIFY_PERM_EVENTS | \
88 				   FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
89 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | \
90 				   FS_OPEN | FS_OPEN_EXEC)
91 
92 /*
93  * This is a list of all events that may get sent with the parent inode as the
94  * @to_tell argument of fsnotify().
95  * It may include events that can be sent to an inode/sb/mount mark, but cannot
96  * be sent to a parent watching children.
97  */
98 #define FS_EVENTS_POSS_TO_PARENT (FS_EVENTS_POSS_ON_CHILD)
99 
100 /* Events that can be reported to backends */
101 #define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
102 			     FS_EVENTS_POSS_ON_CHILD | \
103 			     FS_DELETE_SELF | FS_MOVE_SELF | \
104 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
105 			     FS_ERROR)
106 
107 /* Extra flags that may be reported with event or control handling of events */
108 #define ALL_FSNOTIFY_FLAGS  (FS_ISDIR | FS_EVENT_ON_CHILD | FS_DN_MULTISHOT)
109 
110 #define ALL_FSNOTIFY_BITS   (ALL_FSNOTIFY_EVENTS | ALL_FSNOTIFY_FLAGS)
111 
112 struct fsnotify_group;
113 struct fsnotify_event;
114 struct fsnotify_mark;
115 struct fsnotify_event_private_data;
116 struct fsnotify_fname;
117 struct fsnotify_iter_info;
118 
119 struct mem_cgroup;
120 
121 /*
122  * Each group much define these ops.  The fsnotify infrastructure will call
123  * these operations for each relevant group.
124  *
125  * handle_event - main call for a group to handle an fs event
126  * @group:	group to notify
127  * @mask:	event type and flags
128  * @data:	object that event happened on
129  * @data_type:	type of object for fanotify_data_XXX() accessors
130  * @dir:	optional directory associated with event -
131  *		if @file_name is not NULL, this is the directory that
132  *		@file_name is relative to
133  * @file_name:	optional file name associated with event
134  * @cookie:	inotify rename cookie
135  * @iter_info:	array of marks from this group that are interested in the event
136  *
137  * handle_inode_event - simple variant of handle_event() for groups that only
138  *		have inode marks and don't have ignore mask
139  * @mark:	mark to notify
140  * @mask:	event type and flags
141  * @inode:	inode that event happened on
142  * @dir:	optional directory associated with event -
143  *		if @file_name is not NULL, this is the directory that
144  *		@file_name is relative to.
145  *		Either @inode or @dir must be non-NULL.
146  * @file_name:	optional file name associated with event
147  * @cookie:	inotify rename cookie
148  *
149  * free_group_priv - called when a group refcnt hits 0 to clean up the private union
150  * freeing_mark - called when a mark is being destroyed for some reason.  The group
151  *		MUST be holding a reference on each mark and that reference must be
152  *		dropped in this function.  inotify uses this function to send
153  *		userspace messages that marks have been removed.
154  */
155 struct fsnotify_ops {
156 	int (*handle_event)(struct fsnotify_group *group, u32 mask,
157 			    const void *data, int data_type, struct inode *dir,
158 			    const struct qstr *file_name, u32 cookie,
159 			    struct fsnotify_iter_info *iter_info);
160 	int (*handle_inode_event)(struct fsnotify_mark *mark, u32 mask,
161 			    struct inode *inode, struct inode *dir,
162 			    const struct qstr *file_name, u32 cookie);
163 	void (*free_group_priv)(struct fsnotify_group *group);
164 	void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
165 	void (*free_event)(struct fsnotify_group *group, struct fsnotify_event *event);
166 	/* called on final put+free to free memory */
167 	void (*free_mark)(struct fsnotify_mark *mark);
168 };
169 
170 /*
171  * all of the information about the original object we want to now send to
172  * a group.  If you want to carry more info from the accessing task to the
173  * listener this structure is where you need to be adding fields.
174  */
175 struct fsnotify_event {
176 	struct list_head list;
177 };
178 
179 /*
180  * A group is a "thing" that wants to receive notification about filesystem
181  * events.  The mask holds the subset of event types this group cares about.
182  * refcnt on a group is up to the implementor and at any moment if it goes 0
183  * everything will be cleaned up.
184  */
185 struct fsnotify_group {
186 	const struct fsnotify_ops *ops;	/* how this group handles things */
187 
188 	/*
189 	 * How the refcnt is used is up to each group.  When the refcnt hits 0
190 	 * fsnotify will clean up all of the resources associated with this group.
191 	 * As an example, the dnotify group will always have a refcnt=1 and that
192 	 * will never change.  Inotify, on the other hand, has a group per
193 	 * inotify_init() and the refcnt will hit 0 only when that fd has been
194 	 * closed.
195 	 */
196 	refcount_t refcnt;		/* things with interest in this group */
197 
198 	/* needed to send notification to userspace */
199 	spinlock_t notification_lock;		/* protect the notification_list */
200 	struct list_head notification_list;	/* list of event_holder this group needs to send to userspace */
201 	wait_queue_head_t notification_waitq;	/* read() on the notification file blocks on this waitq */
202 	unsigned int q_len;			/* events on the queue */
203 	unsigned int max_events;		/* maximum events allowed on the list */
204 	/*
205 	 * Valid fsnotify group priorities.  Events are send in order from highest
206 	 * priority to lowest priority.  We default to the lowest priority.
207 	 */
208 	#define FS_PRIO_0	0 /* normal notifiers, no permissions */
209 	#define FS_PRIO_1	1 /* fanotify content based access control */
210 	#define FS_PRIO_2	2 /* fanotify pre-content access */
211 	unsigned int priority;
212 	bool shutdown;		/* group is being shut down, don't queue more events */
213 
214 #define FSNOTIFY_GROUP_USER	0x01 /* user allocated group */
215 #define FSNOTIFY_GROUP_DUPS	0x02 /* allow multiple marks per object */
216 #define FSNOTIFY_GROUP_NOFS	0x04 /* group lock is not direct reclaim safe */
217 	int flags;
218 	unsigned int owner_flags;	/* stored flags of mark_mutex owner */
219 
220 	/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
221 	struct mutex mark_mutex;	/* protect marks_list */
222 	atomic_t user_waits;		/* Number of tasks waiting for user
223 					 * response */
224 	struct list_head marks_list;	/* all inode marks for this group */
225 
226 	struct fasync_struct *fsn_fa;    /* async notification */
227 
228 	struct fsnotify_event *overflow_event;	/* Event we queue when the
229 						 * notification list is too
230 						 * full */
231 
232 	struct mem_cgroup *memcg;	/* memcg to charge allocations */
233 
234 	/* groups can define private fields here or use the void *private */
235 	union {
236 		void *private;
237 #ifdef CONFIG_INOTIFY_USER
238 		struct inotify_group_private_data {
239 			spinlock_t	idr_lock;
240 			struct idr      idr;
241 			struct ucounts *ucounts;
242 		} inotify_data;
243 #endif
244 #ifdef CONFIG_FANOTIFY
245 		struct fanotify_group_private_data {
246 			/* Hash table of events for merge */
247 			struct hlist_head *merge_hash;
248 			/* allows a group to block waiting for a userspace response */
249 			struct list_head access_list;
250 			wait_queue_head_t access_waitq;
251 			int flags;           /* flags from fanotify_init() */
252 			int f_flags; /* event_f_flags from fanotify_init() */
253 			struct ucounts *ucounts;
254 			mempool_t error_events_pool;
255 		} fanotify_data;
256 #endif /* CONFIG_FANOTIFY */
257 	};
258 };
259 
260 /*
261  * These helpers are used to prevent deadlock when reclaiming inodes with
262  * evictable marks of the same group that is allocating a new mark.
263  */
fsnotify_group_lock(struct fsnotify_group * group)264 static inline void fsnotify_group_lock(struct fsnotify_group *group)
265 {
266 	mutex_lock(&group->mark_mutex);
267 	if (group->flags & FSNOTIFY_GROUP_NOFS)
268 		group->owner_flags = memalloc_nofs_save();
269 }
270 
fsnotify_group_unlock(struct fsnotify_group * group)271 static inline void fsnotify_group_unlock(struct fsnotify_group *group)
272 {
273 	if (group->flags & FSNOTIFY_GROUP_NOFS)
274 		memalloc_nofs_restore(group->owner_flags);
275 	mutex_unlock(&group->mark_mutex);
276 }
277 
fsnotify_group_assert_locked(struct fsnotify_group * group)278 static inline void fsnotify_group_assert_locked(struct fsnotify_group *group)
279 {
280 	WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
281 	if (group->flags & FSNOTIFY_GROUP_NOFS)
282 		WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS));
283 }
284 
285 /* When calling fsnotify tell it if the data is a path or inode */
286 enum fsnotify_data_type {
287 	FSNOTIFY_EVENT_NONE,
288 	FSNOTIFY_EVENT_PATH,
289 	FSNOTIFY_EVENT_INODE,
290 	FSNOTIFY_EVENT_DENTRY,
291 	FSNOTIFY_EVENT_ERROR,
292 };
293 
294 struct fs_error_report {
295 	int error;
296 	struct inode *inode;
297 	struct super_block *sb;
298 };
299 
fsnotify_data_inode(const void * data,int data_type)300 static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
301 {
302 	switch (data_type) {
303 	case FSNOTIFY_EVENT_INODE:
304 		return (struct inode *)data;
305 	case FSNOTIFY_EVENT_DENTRY:
306 		return d_inode(data);
307 	case FSNOTIFY_EVENT_PATH:
308 		return d_inode(((const struct path *)data)->dentry);
309 	case FSNOTIFY_EVENT_ERROR:
310 		return ((struct fs_error_report *)data)->inode;
311 	default:
312 		return NULL;
313 	}
314 }
315 
fsnotify_data_dentry(const void * data,int data_type)316 static inline struct dentry *fsnotify_data_dentry(const void *data, int data_type)
317 {
318 	switch (data_type) {
319 	case FSNOTIFY_EVENT_DENTRY:
320 		/* Non const is needed for dget() */
321 		return (struct dentry *)data;
322 	case FSNOTIFY_EVENT_PATH:
323 		return ((const struct path *)data)->dentry;
324 	default:
325 		return NULL;
326 	}
327 }
328 
fsnotify_data_path(const void * data,int data_type)329 static inline const struct path *fsnotify_data_path(const void *data,
330 						    int data_type)
331 {
332 	switch (data_type) {
333 	case FSNOTIFY_EVENT_PATH:
334 		return data;
335 	default:
336 		return NULL;
337 	}
338 }
339 
fsnotify_data_sb(const void * data,int data_type)340 static inline struct super_block *fsnotify_data_sb(const void *data,
341 						   int data_type)
342 {
343 	switch (data_type) {
344 	case FSNOTIFY_EVENT_INODE:
345 		return ((struct inode *)data)->i_sb;
346 	case FSNOTIFY_EVENT_DENTRY:
347 		return ((struct dentry *)data)->d_sb;
348 	case FSNOTIFY_EVENT_PATH:
349 		return ((const struct path *)data)->dentry->d_sb;
350 	case FSNOTIFY_EVENT_ERROR:
351 		return ((struct fs_error_report *) data)->sb;
352 	default:
353 		return NULL;
354 	}
355 }
356 
fsnotify_data_error_report(const void * data,int data_type)357 static inline struct fs_error_report *fsnotify_data_error_report(
358 							const void *data,
359 							int data_type)
360 {
361 	switch (data_type) {
362 	case FSNOTIFY_EVENT_ERROR:
363 		return (struct fs_error_report *) data;
364 	default:
365 		return NULL;
366 	}
367 }
368 
369 /*
370  * Index to merged marks iterator array that correlates to a type of watch.
371  * The type of watched object can be deduced from the iterator type, but not
372  * the other way around, because an event can match different watched objects
373  * of the same object type.
374  * For example, both parent and child are watching an object of type inode.
375  */
376 enum fsnotify_iter_type {
377 	FSNOTIFY_ITER_TYPE_INODE,
378 	FSNOTIFY_ITER_TYPE_VFSMOUNT,
379 	FSNOTIFY_ITER_TYPE_SB,
380 	FSNOTIFY_ITER_TYPE_PARENT,
381 	FSNOTIFY_ITER_TYPE_INODE2,
382 	FSNOTIFY_ITER_TYPE_COUNT
383 };
384 
385 /* The type of object that a mark is attached to */
386 enum fsnotify_obj_type {
387 	FSNOTIFY_OBJ_TYPE_ANY = -1,
388 	FSNOTIFY_OBJ_TYPE_INODE,
389 	FSNOTIFY_OBJ_TYPE_VFSMOUNT,
390 	FSNOTIFY_OBJ_TYPE_SB,
391 	FSNOTIFY_OBJ_TYPE_COUNT,
392 	FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT
393 };
394 
fsnotify_valid_obj_type(unsigned int obj_type)395 static inline bool fsnotify_valid_obj_type(unsigned int obj_type)
396 {
397 	return (obj_type < FSNOTIFY_OBJ_TYPE_COUNT);
398 }
399 
400 struct fsnotify_iter_info {
401 	struct fsnotify_mark *marks[FSNOTIFY_ITER_TYPE_COUNT];
402 	struct fsnotify_group *current_group;
403 	unsigned int report_mask;
404 	int srcu_idx;
405 };
406 
fsnotify_iter_should_report_type(struct fsnotify_iter_info * iter_info,int iter_type)407 static inline bool fsnotify_iter_should_report_type(
408 		struct fsnotify_iter_info *iter_info, int iter_type)
409 {
410 	return (iter_info->report_mask & (1U << iter_type));
411 }
412 
fsnotify_iter_set_report_type(struct fsnotify_iter_info * iter_info,int iter_type)413 static inline void fsnotify_iter_set_report_type(
414 		struct fsnotify_iter_info *iter_info, int iter_type)
415 {
416 	iter_info->report_mask |= (1U << iter_type);
417 }
418 
fsnotify_iter_mark(struct fsnotify_iter_info * iter_info,int iter_type)419 static inline struct fsnotify_mark *fsnotify_iter_mark(
420 		struct fsnotify_iter_info *iter_info, int iter_type)
421 {
422 	if (fsnotify_iter_should_report_type(iter_info, iter_type))
423 		return iter_info->marks[iter_type];
424 	return NULL;
425 }
426 
fsnotify_iter_step(struct fsnotify_iter_info * iter,int type,struct fsnotify_mark ** markp)427 static inline int fsnotify_iter_step(struct fsnotify_iter_info *iter, int type,
428 				     struct fsnotify_mark **markp)
429 {
430 	while (type < FSNOTIFY_ITER_TYPE_COUNT) {
431 		*markp = fsnotify_iter_mark(iter, type);
432 		if (*markp)
433 			break;
434 		type++;
435 	}
436 	return type;
437 }
438 
439 #define FSNOTIFY_ITER_FUNCS(name, NAME) \
440 static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \
441 		struct fsnotify_iter_info *iter_info) \
442 { \
443 	return fsnotify_iter_mark(iter_info, FSNOTIFY_ITER_TYPE_##NAME); \
444 }
445 
446 FSNOTIFY_ITER_FUNCS(inode, INODE)
447 FSNOTIFY_ITER_FUNCS(parent, PARENT)
448 FSNOTIFY_ITER_FUNCS(vfsmount, VFSMOUNT)
449 FSNOTIFY_ITER_FUNCS(sb, SB)
450 
451 #define fsnotify_foreach_iter_type(type) \
452 	for (type = 0; type < FSNOTIFY_ITER_TYPE_COUNT; type++)
453 #define fsnotify_foreach_iter_mark_type(iter, mark, type) \
454 	for (type = 0; \
455 	     type = fsnotify_iter_step(iter, type, &mark), \
456 	     type < FSNOTIFY_ITER_TYPE_COUNT; \
457 	     type++)
458 
459 /*
460  * fsnotify_connp_t is what we embed in objects which connector can be attached
461  * to. fsnotify_connp_t * is how we refer from connector back to object.
462  */
463 struct fsnotify_mark_connector;
464 typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;
465 
466 /*
467  * Inode/vfsmount/sb point to this structure which tracks all marks attached to
468  * the inode/vfsmount/sb. The reference to inode/vfsmount/sb is held by this
469  * structure. We destroy this structure when there are no more marks attached
470  * to it. The structure is protected by fsnotify_mark_srcu.
471  */
472 struct fsnotify_mark_connector {
473 	spinlock_t lock;
474 	unsigned short type;	/* Type of object [lock] */
475 #define FSNOTIFY_CONN_FLAG_HAS_FSID	0x01
476 #define FSNOTIFY_CONN_FLAG_HAS_IREF	0x02
477 	unsigned short flags;	/* flags [lock] */
478 	__kernel_fsid_t fsid;	/* fsid of filesystem containing object */
479 	union {
480 		/* Object pointer [lock] */
481 		fsnotify_connp_t *obj;
482 		/* Used listing heads to free after srcu period expires */
483 		struct fsnotify_mark_connector *destroy_next;
484 	};
485 	struct hlist_head list;
486 };
487 
488 /*
489  * A mark is simply an object attached to an in core inode which allows an
490  * fsnotify listener to indicate they are either no longer interested in events
491  * of a type matching mask or only interested in those events.
492  *
493  * These are flushed when an inode is evicted from core and may be flushed
494  * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
495  * users (such as dnotify) will flush these when the open fd is closed and not
496  * at inode eviction or modification.
497  *
498  * Text in brackets is showing the lock(s) protecting modifications of a
499  * particular entry. obj_lock means either inode->i_lock or
500  * mnt->mnt_root->d_lock depending on the mark type.
501  */
502 struct fsnotify_mark {
503 	/* Mask this mark is for [mark->lock, group->mark_mutex] */
504 	__u32 mask;
505 	/* We hold one for presence in g_list. Also one ref for each 'thing'
506 	 * in kernel that found and may be using this mark. */
507 	refcount_t refcnt;
508 	/* Group this mark is for. Set on mark creation, stable until last ref
509 	 * is dropped */
510 	struct fsnotify_group *group;
511 	/* List of marks by group->marks_list. Also reused for queueing
512 	 * mark into destroy_list when it's waiting for the end of SRCU period
513 	 * before it can be freed. [group->mark_mutex] */
514 	struct list_head g_list;
515 	/* Protects inode / mnt pointers, flags, masks */
516 	spinlock_t lock;
517 	/* List of marks for inode / vfsmount [connector->lock, mark ref] */
518 	struct hlist_node obj_list;
519 	/* Head of list of marks for an object [mark ref] */
520 	struct fsnotify_mark_connector *connector;
521 	/* Events types and flags to ignore [mark->lock, group->mark_mutex] */
522 	__u32 ignore_mask;
523 	/* General fsnotify mark flags */
524 #define FSNOTIFY_MARK_FLAG_ALIVE		0x0001
525 #define FSNOTIFY_MARK_FLAG_ATTACHED		0x0002
526 	/* inotify mark flags */
527 #define FSNOTIFY_MARK_FLAG_EXCL_UNLINK		0x0010
528 #define FSNOTIFY_MARK_FLAG_IN_ONESHOT		0x0020
529 	/* fanotify mark flags */
530 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x0100
531 #define FSNOTIFY_MARK_FLAG_NO_IREF		0x0200
532 #define FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS	0x0400
533 	unsigned int flags;		/* flags [mark->lock] */
534 };
535 
536 #ifdef CONFIG_FSNOTIFY
537 
538 /* called from the vfs helpers */
539 
540 /* main fsnotify call to send events */
541 extern int fsnotify(__u32 mask, const void *data, int data_type,
542 		    struct inode *dir, const struct qstr *name,
543 		    struct inode *inode, u32 cookie);
544 extern int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
545 			   int data_type);
546 extern void __fsnotify_inode_delete(struct inode *inode);
547 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
548 extern void fsnotify_sb_delete(struct super_block *sb);
549 extern u32 fsnotify_get_cookie(void);
550 
fsnotify_parent_needed_mask(__u32 mask)551 static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
552 {
553 	/* FS_EVENT_ON_CHILD is set on marks that want parent/name info */
554 	if (!(mask & FS_EVENT_ON_CHILD))
555 		return 0;
556 	/*
557 	 * This object might be watched by a mark that cares about parent/name
558 	 * info, does it care about the specific set of events that can be
559 	 * reported with parent/name info?
560 	 */
561 	return mask & FS_EVENTS_POSS_TO_PARENT;
562 }
563 
fsnotify_inode_watches_children(struct inode * inode)564 static inline int fsnotify_inode_watches_children(struct inode *inode)
565 {
566 	__u32 parent_mask = READ_ONCE(inode->i_fsnotify_mask);
567 
568 	/* FS_EVENT_ON_CHILD is set if the inode may care */
569 	if (!(parent_mask & FS_EVENT_ON_CHILD))
570 		return 0;
571 	/* this inode might care about child events, does it care about the
572 	 * specific set of events that can happen on a child? */
573 	return parent_mask & FS_EVENTS_POSS_ON_CHILD;
574 }
575 
576 /*
577  * Update the dentry with a flag indicating the interest of its parent to receive
578  * filesystem events when those events happens to this dentry->d_inode.
579  */
fsnotify_update_flags(struct dentry * dentry)580 static inline void fsnotify_update_flags(struct dentry *dentry)
581 {
582 	assert_spin_locked(&dentry->d_lock);
583 
584 	/*
585 	 * Serialisation of setting PARENT_WATCHED on the dentries is provided
586 	 * by d_lock. If inotify_inode_watched changes after we have taken
587 	 * d_lock, the following fsnotify_set_children_dentry_flags call will
588 	 * find our entry, so it will spin until we complete here, and update
589 	 * us with the new state.
590 	 */
591 	if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
592 		dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
593 	else
594 		dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
595 }
596 
597 /* called from fsnotify listeners, such as fanotify or dnotify */
598 
599 /* create a new group */
600 extern struct fsnotify_group *fsnotify_alloc_group(
601 				const struct fsnotify_ops *ops,
602 				int flags);
603 /* get reference to a group */
604 extern void fsnotify_get_group(struct fsnotify_group *group);
605 /* drop reference on a group from fsnotify_alloc_group */
606 extern void fsnotify_put_group(struct fsnotify_group *group);
607 /* group destruction begins, stop queuing new events */
608 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
609 /* destroy group */
610 extern void fsnotify_destroy_group(struct fsnotify_group *group);
611 /* fasync handler function */
612 extern int fsnotify_fasync(int fd, struct file *file, int on);
613 /* Free event from memory */
614 extern void fsnotify_destroy_event(struct fsnotify_group *group,
615 				   struct fsnotify_event *event);
616 /* attach the event to the group notification queue */
617 extern int fsnotify_insert_event(struct fsnotify_group *group,
618 				 struct fsnotify_event *event,
619 				 int (*merge)(struct fsnotify_group *,
620 					      struct fsnotify_event *),
621 				 void (*insert)(struct fsnotify_group *,
622 						struct fsnotify_event *));
623 
fsnotify_add_event(struct fsnotify_group * group,struct fsnotify_event * event,int (* merge)(struct fsnotify_group *,struct fsnotify_event *))624 static inline int fsnotify_add_event(struct fsnotify_group *group,
625 				     struct fsnotify_event *event,
626 				     int (*merge)(struct fsnotify_group *,
627 						  struct fsnotify_event *))
628 {
629 	return fsnotify_insert_event(group, event, merge, NULL);
630 }
631 
632 /* Queue overflow event to a notification group */
fsnotify_queue_overflow(struct fsnotify_group * group)633 static inline void fsnotify_queue_overflow(struct fsnotify_group *group)
634 {
635 	fsnotify_add_event(group, group->overflow_event, NULL);
636 }
637 
fsnotify_is_overflow_event(u32 mask)638 static inline bool fsnotify_is_overflow_event(u32 mask)
639 {
640 	return mask & FS_Q_OVERFLOW;
641 }
642 
fsnotify_notify_queue_is_empty(struct fsnotify_group * group)643 static inline bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
644 {
645 	assert_spin_locked(&group->notification_lock);
646 
647 	return list_empty(&group->notification_list);
648 }
649 
650 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
651 /* return, but do not dequeue the first event on the notification queue */
652 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
653 /* return AND dequeue the first event on the notification queue */
654 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
655 /* Remove event queued in the notification list */
656 extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
657 					 struct fsnotify_event *event);
658 
659 /* functions used to manipulate the marks attached to inodes */
660 
661 /*
662  * Canonical "ignore mask" including event flags.
663  *
664  * Note the subtle semantic difference from the legacy ->ignored_mask.
665  * ->ignored_mask traditionally only meant which events should be ignored,
666  * while ->ignore_mask also includes flags regarding the type of objects on
667  * which events should be ignored.
668  */
fsnotify_ignore_mask(struct fsnotify_mark * mark)669 static inline __u32 fsnotify_ignore_mask(struct fsnotify_mark *mark)
670 {
671 	__u32 ignore_mask = mark->ignore_mask;
672 
673 	/* The event flags in ignore mask take effect */
674 	if (mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
675 		return ignore_mask;
676 
677 	/*
678 	 * Legacy behavior:
679 	 * - Always ignore events on dir
680 	 * - Ignore events on child if parent is watching children
681 	 */
682 	ignore_mask |= FS_ISDIR;
683 	ignore_mask &= ~FS_EVENT_ON_CHILD;
684 	ignore_mask |= mark->mask & FS_EVENT_ON_CHILD;
685 
686 	return ignore_mask;
687 }
688 
689 /* Legacy ignored_mask - only event types to ignore */
fsnotify_ignored_events(struct fsnotify_mark * mark)690 static inline __u32 fsnotify_ignored_events(struct fsnotify_mark *mark)
691 {
692 	return mark->ignore_mask & ALL_FSNOTIFY_EVENTS;
693 }
694 
695 /*
696  * Check if mask (or ignore mask) should be applied depending if victim is a
697  * directory and whether it is reported to a watching parent.
698  */
fsnotify_mask_applicable(__u32 mask,bool is_dir,int iter_type)699 static inline bool fsnotify_mask_applicable(__u32 mask, bool is_dir,
700 					    int iter_type)
701 {
702 	/* Should mask be applied to a directory? */
703 	if (is_dir && !(mask & FS_ISDIR))
704 		return false;
705 
706 	/* Should mask be applied to a child? */
707 	if (iter_type == FSNOTIFY_ITER_TYPE_PARENT &&
708 	    !(mask & FS_EVENT_ON_CHILD))
709 		return false;
710 
711 	return true;
712 }
713 
714 /*
715  * Effective ignore mask taking into account if event victim is a
716  * directory and whether it is reported to a watching parent.
717  */
fsnotify_effective_ignore_mask(struct fsnotify_mark * mark,bool is_dir,int iter_type)718 static inline __u32 fsnotify_effective_ignore_mask(struct fsnotify_mark *mark,
719 						   bool is_dir, int iter_type)
720 {
721 	__u32 ignore_mask = fsnotify_ignored_events(mark);
722 
723 	if (!ignore_mask)
724 		return 0;
725 
726 	/* For non-dir and non-child, no need to consult the event flags */
727 	if (!is_dir && iter_type != FSNOTIFY_ITER_TYPE_PARENT)
728 		return ignore_mask;
729 
730 	ignore_mask = fsnotify_ignore_mask(mark);
731 	if (!fsnotify_mask_applicable(ignore_mask, is_dir, iter_type))
732 		return 0;
733 
734 	return ignore_mask & ALL_FSNOTIFY_EVENTS;
735 }
736 
737 /* Get mask for calculating object interest taking ignore mask into account */
fsnotify_calc_mask(struct fsnotify_mark * mark)738 static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
739 {
740 	__u32 mask = mark->mask;
741 
742 	if (!fsnotify_ignored_events(mark))
743 		return mask;
744 
745 	/* Interest in FS_MODIFY may be needed for clearing ignore mask */
746 	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
747 		mask |= FS_MODIFY;
748 
749 	/*
750 	 * If mark is interested in ignoring events on children, the object must
751 	 * show interest in those events for fsnotify_parent() to notice it.
752 	 */
753 	return mask | mark->ignore_mask;
754 }
755 
756 /* Get mask of events for a list of marks */
757 extern __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn);
758 /* Calculate mask of events for a list of marks */
759 extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
760 extern void fsnotify_init_mark(struct fsnotify_mark *mark,
761 			       struct fsnotify_group *group);
762 /* Find mark belonging to given group in the list of marks */
763 extern struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
764 						struct fsnotify_group *group);
765 /* attach the mark to the object */
766 extern int fsnotify_add_mark(struct fsnotify_mark *mark,
767 			     fsnotify_connp_t *connp, unsigned int obj_type,
768 			     int add_flags, __kernel_fsid_t *fsid);
769 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
770 				    fsnotify_connp_t *connp,
771 				    unsigned int obj_type, int add_flags,
772 				    __kernel_fsid_t *fsid);
773 
774 /* attach the mark to the inode */
fsnotify_add_inode_mark(struct fsnotify_mark * mark,struct inode * inode,int add_flags)775 static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
776 					  struct inode *inode,
777 					  int add_flags)
778 {
779 	return fsnotify_add_mark(mark, &inode->i_fsnotify_marks,
780 				 FSNOTIFY_OBJ_TYPE_INODE, add_flags, NULL);
781 }
fsnotify_add_inode_mark_locked(struct fsnotify_mark * mark,struct inode * inode,int add_flags)782 static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark,
783 						 struct inode *inode,
784 						 int add_flags)
785 {
786 	return fsnotify_add_mark_locked(mark, &inode->i_fsnotify_marks,
787 					FSNOTIFY_OBJ_TYPE_INODE, add_flags,
788 					NULL);
789 }
790 
791 /* given a group and a mark, flag mark to be freed when all references are dropped */
792 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
793 				  struct fsnotify_group *group);
794 /* detach mark from inode / mount list, group list, drop inode reference */
795 extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
796 /* free mark */
797 extern void fsnotify_free_mark(struct fsnotify_mark *mark);
798 /* Wait until all marks queued for destruction are destroyed */
799 extern void fsnotify_wait_marks_destroyed(void);
800 /* Clear all of the marks of a group attached to a given object type */
801 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
802 					  unsigned int obj_type);
803 /* run all the marks in a group, and clear all of the vfsmount marks */
fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group * group)804 static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
805 {
806 	fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT);
807 }
808 /* run all the marks in a group, and clear all of the inode marks */
fsnotify_clear_inode_marks_by_group(struct fsnotify_group * group)809 static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
810 {
811 	fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE);
812 }
813 /* run all the marks in a group, and clear all of the sn marks */
fsnotify_clear_sb_marks_by_group(struct fsnotify_group * group)814 static inline void fsnotify_clear_sb_marks_by_group(struct fsnotify_group *group)
815 {
816 	fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_SB);
817 }
818 extern void fsnotify_get_mark(struct fsnotify_mark *mark);
819 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
820 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
821 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
822 
fsnotify_init_event(struct fsnotify_event * event)823 static inline void fsnotify_init_event(struct fsnotify_event *event)
824 {
825 	INIT_LIST_HEAD(&event->list);
826 }
827 
828 #else
829 
fsnotify(__u32 mask,const void * data,int data_type,struct inode * dir,const struct qstr * name,struct inode * inode,u32 cookie)830 static inline int fsnotify(__u32 mask, const void *data, int data_type,
831 			   struct inode *dir, const struct qstr *name,
832 			   struct inode *inode, u32 cookie)
833 {
834 	return 0;
835 }
836 
__fsnotify_parent(struct dentry * dentry,__u32 mask,const void * data,int data_type)837 static inline int __fsnotify_parent(struct dentry *dentry, __u32 mask,
838 				  const void *data, int data_type)
839 {
840 	return 0;
841 }
842 
__fsnotify_inode_delete(struct inode * inode)843 static inline void __fsnotify_inode_delete(struct inode *inode)
844 {}
845 
__fsnotify_vfsmount_delete(struct vfsmount * mnt)846 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
847 {}
848 
fsnotify_sb_delete(struct super_block * sb)849 static inline void fsnotify_sb_delete(struct super_block *sb)
850 {}
851 
fsnotify_update_flags(struct dentry * dentry)852 static inline void fsnotify_update_flags(struct dentry *dentry)
853 {}
854 
fsnotify_get_cookie(void)855 static inline u32 fsnotify_get_cookie(void)
856 {
857 	return 0;
858 }
859 
fsnotify_unmount_inodes(struct super_block * sb)860 static inline void fsnotify_unmount_inodes(struct super_block *sb)
861 {}
862 
863 #endif	/* CONFIG_FSNOTIFY */
864 
865 #endif	/* __KERNEL __ */
866 
867 #endif	/* __LINUX_FSNOTIFY_BACKEND_H */
868