include/linux/fsnotify_backend.h

   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                             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 */