1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Filesystem access notification for Linux 4 * 5 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <[email protected]> 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 23 /* 24 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily 25 * convert between them. dnotify only needs conversion at watch creation 26 * so no perf loss there. fanotify isn't defined yet, so it can use the 27 * wholes if it needs more events. 28 */ 29 #define FS_ACCESS 0x00000001 /* File was accessed */ 30 #define FS_MODIFY 0x00000002 /* File was modified */ 31 #define FS_ATTRIB 0x00000004 /* Metadata changed */ 32 #define FS_CLOSE_WRITE 0x00000008 /* Writtable file was closed */ 33 #define FS_CLOSE_NOWRITE 0x00000010 /* Unwrittable file closed */ 34 #define FS_OPEN 0x00000020 /* File was opened */ 35 #define FS_MOVED_FROM 0x00000040 /* File was moved from X */ 36 #define FS_MOVED_TO 0x00000080 /* File was moved to Y */ 37 #define FS_CREATE 0x00000100 /* Subfile was created */ 38 #define FS_DELETE 0x00000200 /* Subfile was deleted */ 39 #define FS_DELETE_SELF 0x00000400 /* Self was deleted */ 40 #define FS_MOVE_SELF 0x00000800 /* Self was moved */ 41 42 #define FS_UNMOUNT 0x00002000 /* inode on umount fs */ 43 #define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */ 44 #define FS_IN_IGNORED 0x00008000 /* last inotify event here */ 45 46 #define FS_OPEN_PERM 0x00010000 /* open event in an permission hook */ 47 #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ 48 49 #define FS_EXCL_UNLINK 0x04000000 /* do not send events if object is unlinked */ 50 #define FS_ISDIR 0x40000000 /* event occurred against dir */ 51 #define FS_IN_ONESHOT 0x80000000 /* only send event once */ 52 53 #define FS_DN_RENAME 0x10000000 /* file renamed */ 54 #define FS_DN_MULTISHOT 0x20000000 /* dnotify multishot */ 55 56 /* This inode cares about things that happen to its children. Always set for 57 * dnotify and inotify. */ 58 #define FS_EVENT_ON_CHILD 0x08000000 59 60 /* This is a list of all events that may get sent to a parernt based on fs event 61 * happening to inodes inside that directory */ 62 #define FS_EVENTS_POSS_ON_CHILD (FS_ACCESS | FS_MODIFY | FS_ATTRIB |\ 63 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\ 64 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\ 65 FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM) 66 67 #define FS_MOVE (FS_MOVED_FROM | FS_MOVED_TO) 68 69 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM) 70 71 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \ 72 FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \ 73 FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \ 74 FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \ 75 FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \ 76 FS_OPEN_PERM | FS_ACCESS_PERM | FS_EXCL_UNLINK | \ 77 FS_ISDIR | FS_IN_ONESHOT | FS_DN_RENAME | \ 78 FS_DN_MULTISHOT | FS_EVENT_ON_CHILD) 79 80 struct fsnotify_group; 81 struct fsnotify_event; 82 struct fsnotify_mark; 83 struct fsnotify_event_private_data; 84 struct fsnotify_fname; 85 struct fsnotify_iter_info; 86 87 /* 88 * Each group much define these ops. The fsnotify infrastructure will call 89 * these operations for each relevant group. 90 * 91 * handle_event - main call for a group to handle an fs event 92 * free_group_priv - called when a group refcnt hits 0 to clean up the private union 93 * freeing_mark - called when a mark is being destroyed for some reason. The group 94 * MUST be holding a reference on each mark and that reference must be 95 * dropped in this function. inotify uses this function to send 96 * userspace messages that marks have been removed. 97 */ 98 struct fsnotify_ops { 99 int (*handle_event)(struct fsnotify_group *group, 100 struct inode *inode, 101 struct fsnotify_mark *inode_mark, 102 struct fsnotify_mark *vfsmount_mark, 103 u32 mask, const void *data, int data_type, 104 const unsigned char *file_name, u32 cookie, 105 struct fsnotify_iter_info *iter_info); 106 void (*free_group_priv)(struct fsnotify_group *group); 107 void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group); 108 void (*free_event)(struct fsnotify_event *event); 109 /* called on final put+free to free memory */ 110 void (*free_mark)(struct fsnotify_mark *mark); 111 }; 112 113 /* 114 * all of the information about the original object we want to now send to 115 * a group. If you want to carry more info from the accessing task to the 116 * listener this structure is where you need to be adding fields. 117 */ 118 struct fsnotify_event { 119 struct list_head list; 120 /* inode may ONLY be dereferenced during handle_event(). */ 121 struct inode *inode; /* either the inode the event happened to or its parent */ 122 u32 mask; /* the type of access, bitwise OR for FS_* event types */ 123 }; 124 125 /* 126 * A group is a "thing" that wants to receive notification about filesystem 127 * events. The mask holds the subset of event types this group cares about. 128 * refcnt on a group is up to the implementor and at any moment if it goes 0 129 * everything will be cleaned up. 130 */ 131 struct fsnotify_group { 132 /* 133 * How the refcnt is used is up to each group. When the refcnt hits 0 134 * fsnotify will clean up all of the resources associated with this group. 135 * As an example, the dnotify group will always have a refcnt=1 and that 136 * will never change. Inotify, on the other hand, has a group per 137 * inotify_init() and the refcnt will hit 0 only when that fd has been 138 * closed. 139 */ 140 refcount_t refcnt; /* things with interest in this group */ 141 142 const struct fsnotify_ops *ops; /* how this group handles things */ 143 144 /* needed to send notification to userspace */ 145 spinlock_t notification_lock; /* protect the notification_list */ 146 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */ 147 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */ 148 unsigned int q_len; /* events on the queue */ 149 unsigned int max_events; /* maximum events allowed on the list */ 150 /* 151 * Valid fsnotify group priorities. Events are send in order from highest 152 * priority to lowest priority. We default to the lowest priority. 153 */ 154 #define FS_PRIO_0 0 /* normal notifiers, no permissions */ 155 #define FS_PRIO_1 1 /* fanotify content based access control */ 156 #define FS_PRIO_2 2 /* fanotify pre-content access */ 157 unsigned int priority; 158 bool shutdown; /* group is being shut down, don't queue more events */ 159 160 /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */ 161 struct mutex mark_mutex; /* protect marks_list */ 162 atomic_t num_marks; /* 1 for each mark and 1 for not being 163 * past the point of no return when freeing 164 * a group */ 165 struct list_head marks_list; /* all inode marks for this group */ 166 167 struct fasync_struct *fsn_fa; /* async notification */ 168 169 struct fsnotify_event *overflow_event; /* Event we queue when the 170 * notification list is too 171 * full */ 172 atomic_t user_waits; /* Number of tasks waiting for user 173 * response */ 174 175 /* groups can define private fields here or use the void *private */ 176 union { 177 void *private; 178 #ifdef CONFIG_INOTIFY_USER 179 struct inotify_group_private_data { 180 spinlock_t idr_lock; 181 struct idr idr; 182 struct ucounts *ucounts; 183 } inotify_data; 184 #endif 185 #ifdef CONFIG_FANOTIFY 186 struct fanotify_group_private_data { 187 /* allows a group to block waiting for a userspace response */ 188 struct list_head access_list; 189 wait_queue_head_t access_waitq; 190 int f_flags; 191 unsigned int max_marks; 192 struct user_struct *user; 193 bool audit; 194 } fanotify_data; 195 #endif /* CONFIG_FANOTIFY */ 196 }; 197 }; 198 199 /* when calling fsnotify tell it if the data is a path or inode */ 200 #define FSNOTIFY_EVENT_NONE 0 201 #define FSNOTIFY_EVENT_PATH 1 202 #define FSNOTIFY_EVENT_INODE 2 203 204 /* 205 * Inode / vfsmount point to this structure which tracks all marks attached to 206 * the inode / vfsmount. The reference to inode / vfsmount is held by this 207 * structure. We destroy this structure when there are no more marks attached 208 * to it. The structure is protected by fsnotify_mark_srcu. 209 */ 210 struct fsnotify_mark_connector { 211 spinlock_t lock; 212 #define FSNOTIFY_OBJ_TYPE_INODE 0x01 213 #define FSNOTIFY_OBJ_TYPE_VFSMOUNT 0x02 214 #define FSNOTIFY_OBJ_ALL_TYPES (FSNOTIFY_OBJ_TYPE_INODE | \ 215 FSNOTIFY_OBJ_TYPE_VFSMOUNT) 216 unsigned int flags; /* Type of object [lock] */ 217 union { /* Object pointer [lock] */ 218 struct inode *inode; 219 struct vfsmount *mnt; 220 }; 221 union { 222 struct hlist_head list; 223 /* Used listing heads to free after srcu period expires */ 224 struct fsnotify_mark_connector *destroy_next; 225 }; 226 }; 227 228 /* 229 * A mark is simply an object attached to an in core inode which allows an 230 * fsnotify listener to indicate they are either no longer interested in events 231 * of a type matching mask or only interested in those events. 232 * 233 * These are flushed when an inode is evicted from core and may be flushed 234 * when the inode is modified (as seen by fsnotify_access). Some fsnotify 235 * users (such as dnotify) will flush these when the open fd is closed and not 236 * at inode eviction or modification. 237 * 238 * Text in brackets is showing the lock(s) protecting modifications of a 239 * particular entry. obj_lock means either inode->i_lock or 240 * mnt->mnt_root->d_lock depending on the mark type. 241 */ 242 struct fsnotify_mark { 243 /* Mask this mark is for [mark->lock, group->mark_mutex] */ 244 __u32 mask; 245 /* We hold one for presence in g_list. Also one ref for each 'thing' 246 * in kernel that found and may be using this mark. */ 247 refcount_t refcnt; 248 /* Group this mark is for. Set on mark creation, stable until last ref 249 * is dropped */ 250 struct fsnotify_group *group; 251 /* List of marks by group->i_fsnotify_marks. Also reused for queueing 252 * mark into destroy_list when it's waiting for the end of SRCU period 253 * before it can be freed. [group->mark_mutex] */ 254 struct list_head g_list; 255 /* Protects inode / mnt pointers, flags, masks */ 256 spinlock_t lock; 257 /* List of marks for inode / vfsmount [connector->lock, mark ref] */ 258 struct hlist_node obj_list; 259 /* Head of list of marks for an object [mark ref] */ 260 struct fsnotify_mark_connector *connector; 261 /* Events types to ignore [mark->lock, group->mark_mutex] */ 262 __u32 ignored_mask; 263 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x01 264 #define FSNOTIFY_MARK_FLAG_ALIVE 0x02 265 #define FSNOTIFY_MARK_FLAG_ATTACHED 0x04 266 unsigned int flags; /* flags [mark->lock] */ 267 }; 268 269 #ifdef CONFIG_FSNOTIFY 270 271 /* called from the vfs helpers */ 272 273 /* main fsnotify call to send events */ 274 extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, 275 const unsigned char *name, u32 cookie); 276 extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask); 277 extern void __fsnotify_inode_delete(struct inode *inode); 278 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt); 279 extern u32 fsnotify_get_cookie(void); 280 281 static inline int fsnotify_inode_watches_children(struct inode *inode) 282 { 283 /* FS_EVENT_ON_CHILD is set if the inode may care */ 284 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD)) 285 return 0; 286 /* this inode might care about child events, does it care about the 287 * specific set of events that can happen on a child? */ 288 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD; 289 } 290 291 /* 292 * Update the dentry with a flag indicating the interest of its parent to receive 293 * filesystem events when those events happens to this dentry->d_inode. 294 */ 295 static inline void fsnotify_update_flags(struct dentry *dentry) 296 { 297 assert_spin_locked(&dentry->d_lock); 298 299 /* 300 * Serialisation of setting PARENT_WATCHED on the dentries is provided 301 * by d_lock. If inotify_inode_watched changes after we have taken 302 * d_lock, the following __fsnotify_update_child_dentry_flags call will 303 * find our entry, so it will spin until we complete here, and update 304 * us with the new state. 305 */ 306 if (fsnotify_inode_watches_children(dentry->d_parent->d_inode)) 307 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; 308 else 309 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; 310 } 311 312 /* called from fsnotify listeners, such as fanotify or dnotify */ 313 314 /* create a new group */ 315 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops); 316 /* get reference to a group */ 317 extern void fsnotify_get_group(struct fsnotify_group *group); 318 /* drop reference on a group from fsnotify_alloc_group */ 319 extern void fsnotify_put_group(struct fsnotify_group *group); 320 /* group destruction begins, stop queuing new events */ 321 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group); 322 /* destroy group */ 323 extern void fsnotify_destroy_group(struct fsnotify_group *group); 324 /* fasync handler function */ 325 extern int fsnotify_fasync(int fd, struct file *file, int on); 326 /* Free event from memory */ 327 extern void fsnotify_destroy_event(struct fsnotify_group *group, 328 struct fsnotify_event *event); 329 /* attach the event to the group notification queue */ 330 extern int fsnotify_add_event(struct fsnotify_group *group, 331 struct fsnotify_event *event, 332 int (*merge)(struct list_head *, 333 struct fsnotify_event *)); 334 /* true if the group notification queue is empty */ 335 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group); 336 /* return, but do not dequeue the first event on the notification queue */ 337 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group); 338 /* return AND dequeue the first event on the notification queue */ 339 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group); 340 341 /* functions used to manipulate the marks attached to inodes */ 342 343 /* Calculate mask of events for a list of marks */ 344 extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn); 345 extern void fsnotify_init_mark(struct fsnotify_mark *mark, 346 struct fsnotify_group *group); 347 /* Find mark belonging to given group in the list of marks */ 348 extern struct fsnotify_mark *fsnotify_find_mark( 349 struct fsnotify_mark_connector __rcu **connp, 350 struct fsnotify_group *group); 351 /* attach the mark to the inode or vfsmount */ 352 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode, 353 struct vfsmount *mnt, int allow_dups); 354 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, 355 struct inode *inode, struct vfsmount *mnt, int allow_dups); 356 /* given a group and a mark, flag mark to be freed when all references are dropped */ 357 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark, 358 struct fsnotify_group *group); 359 /* detach mark from inode / mount list, group list, drop inode reference */ 360 extern void fsnotify_detach_mark(struct fsnotify_mark *mark); 361 /* free mark */ 362 extern void fsnotify_free_mark(struct fsnotify_mark *mark); 363 /* run all the marks in a group, and clear all of the marks attached to given object type */ 364 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type); 365 /* run all the marks in a group, and clear all of the vfsmount marks */ 366 static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group) 367 { 368 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT); 369 } 370 /* run all the marks in a group, and clear all of the inode marks */ 371 static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group) 372 { 373 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE); 374 } 375 extern void fsnotify_get_mark(struct fsnotify_mark *mark); 376 extern void fsnotify_put_mark(struct fsnotify_mark *mark); 377 extern void fsnotify_unmount_inodes(struct super_block *sb); 378 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info); 379 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info); 380 381 /* put here because inotify does some weird stuff when destroying watches */ 382 extern void fsnotify_init_event(struct fsnotify_event *event, 383 struct inode *to_tell, u32 mask); 384 385 #else 386 387 static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, 388 const unsigned char *name, u32 cookie) 389 { 390 return 0; 391 } 392 393 static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) 394 { 395 return 0; 396 } 397 398 static inline void __fsnotify_inode_delete(struct inode *inode) 399 {} 400 401 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 402 {} 403 404 static inline void fsnotify_update_flags(struct dentry *dentry) 405 {} 406 407 static inline u32 fsnotify_get_cookie(void) 408 { 409 return 0; 410 } 411 412 static inline void fsnotify_unmount_inodes(struct super_block *sb) 413 {} 414 415 #endif /* CONFIG_FSNOTIFY */ 416 417 #endif /* __KERNEL __ */ 418 419 #endif /* __LINUX_FSNOTIFY_BACKEND_H */ 420