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 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 u32 mask, const void *data, int data_type, 102 const unsigned char *file_name, u32 cookie, 103 struct fsnotify_iter_info *iter_info); 104 void (*free_group_priv)(struct fsnotify_group *group); 105 void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group); 106 void (*free_event)(struct fsnotify_event *event); 107 /* called on final put+free to free memory */ 108 void (*free_mark)(struct fsnotify_mark *mark); 109 }; 110 111 /* 112 * all of the information about the original object we want to now send to 113 * a group. If you want to carry more info from the accessing task to the 114 * listener this structure is where you need to be adding fields. 115 */ 116 struct fsnotify_event { 117 struct list_head list; 118 /* inode may ONLY be dereferenced during handle_event(). */ 119 struct inode *inode; /* either the inode the event happened to or its parent */ 120 u32 mask; /* the type of access, bitwise OR for FS_* event types */ 121 }; 122 123 /* 124 * A group is a "thing" that wants to receive notification about filesystem 125 * events. The mask holds the subset of event types this group cares about. 126 * refcnt on a group is up to the implementor and at any moment if it goes 0 127 * everything will be cleaned up. 128 */ 129 struct fsnotify_group { 130 /* 131 * How the refcnt is used is up to each group. When the refcnt hits 0 132 * fsnotify will clean up all of the resources associated with this group. 133 * As an example, the dnotify group will always have a refcnt=1 and that 134 * will never change. Inotify, on the other hand, has a group per 135 * inotify_init() and the refcnt will hit 0 only when that fd has been 136 * closed. 137 */ 138 refcount_t refcnt; /* things with interest in this group */ 139 140 const struct fsnotify_ops *ops; /* how this group handles things */ 141 142 /* needed to send notification to userspace */ 143 spinlock_t notification_lock; /* protect the notification_list */ 144 struct list_head notification_list; /* list of event_holder this group needs to send to userspace */ 145 wait_queue_head_t notification_waitq; /* read() on the notification file blocks on this waitq */ 146 unsigned int q_len; /* events on the queue */ 147 unsigned int max_events; /* maximum events allowed on the list */ 148 /* 149 * Valid fsnotify group priorities. Events are send in order from highest 150 * priority to lowest priority. We default to the lowest priority. 151 */ 152 #define FS_PRIO_0 0 /* normal notifiers, no permissions */ 153 #define FS_PRIO_1 1 /* fanotify content based access control */ 154 #define FS_PRIO_2 2 /* fanotify pre-content access */ 155 unsigned int priority; 156 bool shutdown; /* group is being shut down, don't queue more events */ 157 158 /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */ 159 struct mutex mark_mutex; /* protect marks_list */ 160 atomic_t num_marks; /* 1 for each mark and 1 for not being 161 * past the point of no return when freeing 162 * a group */ 163 struct list_head marks_list; /* all inode marks for this group */ 164 165 struct fasync_struct *fsn_fa; /* async notification */ 166 167 struct fsnotify_event *overflow_event; /* Event we queue when the 168 * notification list is too 169 * full */ 170 atomic_t user_waits; /* Number of tasks waiting for user 171 * response */ 172 173 /* groups can define private fields here or use the void *private */ 174 union { 175 void *private; 176 #ifdef CONFIG_INOTIFY_USER 177 struct inotify_group_private_data { 178 spinlock_t idr_lock; 179 struct idr idr; 180 struct ucounts *ucounts; 181 } inotify_data; 182 #endif 183 #ifdef CONFIG_FANOTIFY 184 struct fanotify_group_private_data { 185 /* allows a group to block waiting for a userspace response */ 186 struct list_head access_list; 187 wait_queue_head_t access_waitq; 188 int f_flags; 189 unsigned int max_marks; 190 struct user_struct *user; 191 bool audit; 192 } fanotify_data; 193 #endif /* CONFIG_FANOTIFY */ 194 }; 195 }; 196 197 /* when calling fsnotify tell it if the data is a path or inode */ 198 #define FSNOTIFY_EVENT_NONE 0 199 #define FSNOTIFY_EVENT_PATH 1 200 #define FSNOTIFY_EVENT_INODE 2 201 202 enum fsnotify_obj_type { 203 FSNOTIFY_OBJ_TYPE_INODE, 204 FSNOTIFY_OBJ_TYPE_VFSMOUNT, 205 FSNOTIFY_OBJ_TYPE_COUNT, 206 FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT 207 }; 208 209 #define FSNOTIFY_OBJ_TYPE_INODE_FL (1U << FSNOTIFY_OBJ_TYPE_INODE) 210 #define FSNOTIFY_OBJ_TYPE_VFSMOUNT_FL (1U << FSNOTIFY_OBJ_TYPE_VFSMOUNT) 211 #define FSNOTIFY_OBJ_ALL_TYPES_MASK ((1U << FSNOTIFY_OBJ_TYPE_COUNT) - 1) 212 213 struct fsnotify_iter_info { 214 struct fsnotify_mark *marks[FSNOTIFY_OBJ_TYPE_COUNT]; 215 unsigned int report_mask; 216 int srcu_idx; 217 }; 218 219 static inline bool fsnotify_iter_should_report_type( 220 struct fsnotify_iter_info *iter_info, int type) 221 { 222 return (iter_info->report_mask & (1U << type)); 223 } 224 225 static inline void fsnotify_iter_set_report_type( 226 struct fsnotify_iter_info *iter_info, int type) 227 { 228 iter_info->report_mask |= (1U << type); 229 } 230 231 static inline void fsnotify_iter_set_report_type_mark( 232 struct fsnotify_iter_info *iter_info, int type, 233 struct fsnotify_mark *mark) 234 { 235 iter_info->marks[type] = mark; 236 iter_info->report_mask |= (1U << type); 237 } 238 239 #define FSNOTIFY_ITER_FUNCS(name, NAME) \ 240 static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \ 241 struct fsnotify_iter_info *iter_info) \ 242 { \ 243 return (iter_info->report_mask & FSNOTIFY_OBJ_TYPE_##NAME##_FL) ? \ 244 iter_info->marks[FSNOTIFY_OBJ_TYPE_##NAME] : NULL; \ 245 } 246 247 FSNOTIFY_ITER_FUNCS(inode, INODE) 248 FSNOTIFY_ITER_FUNCS(vfsmount, VFSMOUNT) 249 250 #define fsnotify_foreach_obj_type(type) \ 251 for (type = 0; type < FSNOTIFY_OBJ_TYPE_COUNT; type++) 252 253 /* 254 * Inode / vfsmount point to this structure which tracks all marks attached to 255 * the inode / vfsmount. The reference to inode / vfsmount is held by this 256 * structure. We destroy this structure when there are no more marks attached 257 * to it. The structure is protected by fsnotify_mark_srcu. 258 */ 259 struct fsnotify_mark_connector { 260 spinlock_t lock; 261 unsigned int type; /* Type of object [lock] */ 262 union { /* Object pointer [lock] */ 263 struct inode *inode; 264 struct vfsmount *mnt; 265 /* Used listing heads to free after srcu period expires */ 266 struct fsnotify_mark_connector *destroy_next; 267 }; 268 struct hlist_head list; 269 }; 270 271 /* 272 * A mark is simply an object attached to an in core inode which allows an 273 * fsnotify listener to indicate they are either no longer interested in events 274 * of a type matching mask or only interested in those events. 275 * 276 * These are flushed when an inode is evicted from core and may be flushed 277 * when the inode is modified (as seen by fsnotify_access). Some fsnotify 278 * users (such as dnotify) will flush these when the open fd is closed and not 279 * at inode eviction or modification. 280 * 281 * Text in brackets is showing the lock(s) protecting modifications of a 282 * particular entry. obj_lock means either inode->i_lock or 283 * mnt->mnt_root->d_lock depending on the mark type. 284 */ 285 struct fsnotify_mark { 286 /* Mask this mark is for [mark->lock, group->mark_mutex] */ 287 __u32 mask; 288 /* We hold one for presence in g_list. Also one ref for each 'thing' 289 * in kernel that found and may be using this mark. */ 290 refcount_t refcnt; 291 /* Group this mark is for. Set on mark creation, stable until last ref 292 * is dropped */ 293 struct fsnotify_group *group; 294 /* List of marks by group->marks_list. Also reused for queueing 295 * mark into destroy_list when it's waiting for the end of SRCU period 296 * before it can be freed. [group->mark_mutex] */ 297 struct list_head g_list; 298 /* Protects inode / mnt pointers, flags, masks */ 299 spinlock_t lock; 300 /* List of marks for inode / vfsmount [connector->lock, mark ref] */ 301 struct hlist_node obj_list; 302 /* Head of list of marks for an object [mark ref] */ 303 struct fsnotify_mark_connector *connector; 304 /* Events types to ignore [mark->lock, group->mark_mutex] */ 305 __u32 ignored_mask; 306 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x01 307 #define FSNOTIFY_MARK_FLAG_ALIVE 0x02 308 #define FSNOTIFY_MARK_FLAG_ATTACHED 0x04 309 unsigned int flags; /* flags [mark->lock] */ 310 }; 311 312 #ifdef CONFIG_FSNOTIFY 313 314 /* called from the vfs helpers */ 315 316 /* main fsnotify call to send events */ 317 extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, 318 const unsigned char *name, u32 cookie); 319 extern int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask); 320 extern void __fsnotify_inode_delete(struct inode *inode); 321 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt); 322 extern u32 fsnotify_get_cookie(void); 323 324 static inline int fsnotify_inode_watches_children(struct inode *inode) 325 { 326 /* FS_EVENT_ON_CHILD is set if the inode may care */ 327 if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD)) 328 return 0; 329 /* this inode might care about child events, does it care about the 330 * specific set of events that can happen on a child? */ 331 return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD; 332 } 333 334 /* 335 * Update the dentry with a flag indicating the interest of its parent to receive 336 * filesystem events when those events happens to this dentry->d_inode. 337 */ 338 static inline void fsnotify_update_flags(struct dentry *dentry) 339 { 340 assert_spin_locked(&dentry->d_lock); 341 342 /* 343 * Serialisation of setting PARENT_WATCHED on the dentries is provided 344 * by d_lock. If inotify_inode_watched changes after we have taken 345 * d_lock, the following __fsnotify_update_child_dentry_flags call will 346 * find our entry, so it will spin until we complete here, and update 347 * us with the new state. 348 */ 349 if (fsnotify_inode_watches_children(dentry->d_parent->d_inode)) 350 dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED; 351 else 352 dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED; 353 } 354 355 /* called from fsnotify listeners, such as fanotify or dnotify */ 356 357 /* create a new group */ 358 extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops); 359 /* get reference to a group */ 360 extern void fsnotify_get_group(struct fsnotify_group *group); 361 /* drop reference on a group from fsnotify_alloc_group */ 362 extern void fsnotify_put_group(struct fsnotify_group *group); 363 /* group destruction begins, stop queuing new events */ 364 extern void fsnotify_group_stop_queueing(struct fsnotify_group *group); 365 /* destroy group */ 366 extern void fsnotify_destroy_group(struct fsnotify_group *group); 367 /* fasync handler function */ 368 extern int fsnotify_fasync(int fd, struct file *file, int on); 369 /* Free event from memory */ 370 extern void fsnotify_destroy_event(struct fsnotify_group *group, 371 struct fsnotify_event *event); 372 /* attach the event to the group notification queue */ 373 extern int fsnotify_add_event(struct fsnotify_group *group, 374 struct fsnotify_event *event, 375 int (*merge)(struct list_head *, 376 struct fsnotify_event *)); 377 /* Queue overflow event to a notification group */ 378 static inline void fsnotify_queue_overflow(struct fsnotify_group *group) 379 { 380 fsnotify_add_event(group, group->overflow_event, NULL); 381 } 382 383 /* true if the group notification queue is empty */ 384 extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group); 385 /* return, but do not dequeue the first event on the notification queue */ 386 extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group); 387 /* return AND dequeue the first event on the notification queue */ 388 extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group); 389 390 /* functions used to manipulate the marks attached to inodes */ 391 392 /* Calculate mask of events for a list of marks */ 393 extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn); 394 extern void fsnotify_init_mark(struct fsnotify_mark *mark, 395 struct fsnotify_group *group); 396 /* Find mark belonging to given group in the list of marks */ 397 extern struct fsnotify_mark *fsnotify_find_mark( 398 struct fsnotify_mark_connector __rcu **connp, 399 struct fsnotify_group *group); 400 /* attach the mark to the inode or vfsmount */ 401 extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct inode *inode, 402 struct vfsmount *mnt, int allow_dups); 403 extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, 404 struct inode *inode, struct vfsmount *mnt, 405 int allow_dups); 406 /* attach the mark to the inode */ 407 static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark, 408 struct inode *inode, 409 int allow_dups) 410 { 411 return fsnotify_add_mark(mark, inode, NULL, allow_dups); 412 } 413 static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark, 414 struct inode *inode, 415 int allow_dups) 416 { 417 return fsnotify_add_mark_locked(mark, inode, NULL, allow_dups); 418 } 419 /* given a group and a mark, flag mark to be freed when all references are dropped */ 420 extern void fsnotify_destroy_mark(struct fsnotify_mark *mark, 421 struct fsnotify_group *group); 422 /* detach mark from inode / mount list, group list, drop inode reference */ 423 extern void fsnotify_detach_mark(struct fsnotify_mark *mark); 424 /* free mark */ 425 extern void fsnotify_free_mark(struct fsnotify_mark *mark); 426 /* run all the marks in a group, and clear all of the marks attached to given object type */ 427 extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type); 428 /* run all the marks in a group, and clear all of the vfsmount marks */ 429 static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group) 430 { 431 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT_FL); 432 } 433 /* run all the marks in a group, and clear all of the inode marks */ 434 static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group) 435 { 436 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE_FL); 437 } 438 extern void fsnotify_get_mark(struct fsnotify_mark *mark); 439 extern void fsnotify_put_mark(struct fsnotify_mark *mark); 440 extern void fsnotify_unmount_inodes(struct super_block *sb); 441 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info); 442 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info); 443 444 /* put here because inotify does some weird stuff when destroying watches */ 445 extern void fsnotify_init_event(struct fsnotify_event *event, 446 struct inode *to_tell, u32 mask); 447 448 #else 449 450 static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is, 451 const unsigned char *name, u32 cookie) 452 { 453 return 0; 454 } 455 456 static inline int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) 457 { 458 return 0; 459 } 460 461 static inline void __fsnotify_inode_delete(struct inode *inode) 462 {} 463 464 static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt) 465 {} 466 467 static inline void fsnotify_update_flags(struct dentry *dentry) 468 {} 469 470 static inline u32 fsnotify_get_cookie(void) 471 { 472 return 0; 473 } 474 475 static inline void fsnotify_unmount_inodes(struct super_block *sb) 476 {} 477 478 #endif /* CONFIG_FSNOTIFY */ 479 480 #endif /* __KERNEL __ */ 481 482 #endif /* __LINUX_FSNOTIFY_BACKEND_H */ 483