Commit e252f2ed authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fanotify: introduce FAN_MARK_IGNORE 

This flag is a new way to configure ignore mask which allows adding and
removing the event flags FAN_ONDIR and FAN_EVENT_ON_CHILD in ignore mask.

The legacy FAN_MARK_IGNORED_MASK flag would always ignore events on
directories and would ignore events on children depending on whether
the FAN_EVENT_ON_CHILD flag was set in the (non ignored) mask.

FAN_MARK_IGNORE can be used to ignore events on children without setting
FAN_EVENT_ON_CHILD in the mark's mask and will not ignore events on
directories unconditionally, only when FAN_ONDIR is set in ignore mask.

The new behavior is non-downgradable.  After calling fanotify_mark() with
FAN_MARK_IGNORE once, calling fanotify_mark() with FAN_MARK_IGNORED_MASK
on the same object will return EEXIST error.

Setting the event flags with FAN_MARK_IGNORE on a non-dir inode mark
has no meaning and will return ENOTDIR error.

The meaning of FAN_MARK_IGNORED_SURV_MODIFY is preserved with the new
FAN_MARK_IGNORE flag, but with a few semantic differences:

1. FAN_MARK_IGNORED_SURV_MODIFY is required for filesystem and mount
   marks and on an inode mark on a directory. Omitting this flag
   will return EINVAL or EISDIR error.

2. An ignore mask on a non-directory inode that survives modify could
   never be downgraded to an ignore mask that does not survive modify.
   With new FAN_MARK_IGNORE semantics we make that rule explicit -
   trying to update a surviving ignore mask without the flag
   FAN_MARK_IGNORED_SURV_MODIFY will return EEXIST error.

The conveniene macro FAN_MARK_IGNORE_SURV is added for
(FAN_MARK_IGNORE | FAN_MARK_IGNORED_SURV_MODIFY), because the
common case should use short constant names.

Link: https://lore.kernel.org/r/20220629144210.2983229-4-amir73il@gmail.com


Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 8afd7215

fs/notify/fanotify/fanotify.h

+2 −0
Original line number Diff line number Diff line
@@ -499,6 +499,8 @@ static inline unsigned int fanotify_mark_user_flags(struct fsnotify_mark *mark) 
		mflags |= FAN_MARK_IGNORED_SURV_MODIFY;

	if (mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)

		mflags |= FAN_MARK_EVICTABLE;

	if (mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)

		mflags |= FAN_MARK_IGNORE;



	return mflags;

}

fs/notify/fanotify/fanotify_user.c

+53 −10
Original line number Diff line number Diff line
@@ -1009,7 +1009,7 @@ static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark, 
	mask &= ~umask;

	spin_lock(&fsn_mark->lock);

	oldmask = fsnotify_calc_mask(fsn_mark);

	if (!(flags & FAN_MARK_IGNORED_MASK)) {

	if (!(flags & FANOTIFY_MARK_IGNORE_BITS)) {

		fsn_mark->mask &= ~mask;

	} else {

		fsn_mark->ignore_mask &= ~mask;
@@ -1085,15 +1085,24 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark, 
				       unsigned int fan_flags)

{

	bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);

	unsigned int ignore = fan_flags & FANOTIFY_MARK_IGNORE_BITS;

	bool recalc = false;



	/*

	 * When using FAN_MARK_IGNORE for the first time, mark starts using

	 * independent event flags in ignore mask.  After that, trying to

	 * update the ignore mask with the old FAN_MARK_IGNORED_MASK API

	 * will result in EEXIST error.

	 */

	if (ignore == FAN_MARK_IGNORE)

		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS;



	/*

	 * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to

	 * the removal of the FS_MODIFY bit in calculated mask if it was set

	 * because of an ignore mask that is now going to survive FS_MODIFY.

	 */

	if ((fan_flags & FAN_MARK_IGNORED_MASK) &&

	    (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&

	if (ignore && (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&

	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) {

		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;

		if (!(fsn_mark->mask & FS_MODIFY))
@@ -1120,7 +1129,7 @@ static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark, 
	bool recalc;



	spin_lock(&fsn_mark->lock);

	if (!(fan_flags & FAN_MARK_IGNORED_MASK))

	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))

		fsn_mark->mask |= mask;

	else

		fsn_mark->ignore_mask |= mask;
@@ -1197,6 +1206,24 @@ static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark, 
	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))

		return -EEXIST;



	/*

	 * New ignore mask semantics cannot be downgraded to old semantics.

	 */

	if (fan_flags & FAN_MARK_IGNORED_MASK &&

	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)

		return -EEXIST;



	/*

	 * An ignore mask that survives modify could never be downgraded to not

	 * survive modify.  With new FAN_MARK_IGNORE semantics we make that rule

	 * explicit and return an error when trying to update the ignore mask

	 * without the original FAN_MARK_IGNORED_SURV_MODIFY value.

	 */

	if (fan_flags & FAN_MARK_IGNORE &&

	    !(fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&

	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)

		return -EEXIST;



	return 0;

}
@@ -1231,7 +1258,8 @@ static int fanotify_add_mark(struct fsnotify_group *group, 
	 * Error events are pre-allocated per group, only if strictly

	 * needed (i.e. FAN_FS_ERROR was requested).

	 */

	if (!(fan_flags & FAN_MARK_IGNORED_MASK) && (mask & FAN_FS_ERROR)) {

	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS) &&

	    (mask & FAN_FS_ERROR)) {

		ret = fanotify_group_init_error_pool(group);

		if (ret)

			goto out;
@@ -1275,7 +1303,7 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group, 
	 * an ignore mask, unless that ignore mask is supposed to survive

	 * modification changes anyway.

	 */

	if ((flags & FAN_MARK_IGNORED_MASK) &&

	if ((flags & FANOTIFY_MARK_IGNORE_BITS) &&

	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&

	    inode_is_open_for_write(inode))

		return 0;
@@ -1531,7 +1559,8 @@ static int fanotify_events_supported(struct fsnotify_group *group, 
	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;

	/* Strict validation of events in non-dir inode mask with v5.17+ APIs */

	bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||

				 (mask & FAN_RENAME);

				 (mask & FAN_RENAME) ||

				 (flags & FAN_MARK_IGNORE);



	/*

	 * Some filesystems such as 'proc' acquire unusual locks when opening
@@ -1569,7 +1598,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;

	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;

	unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;

	bool ignore = flags & FAN_MARK_IGNORED_MASK;

	unsigned int ignore = flags & FANOTIFY_MARK_IGNORE_BITS;

	unsigned int obj_type, fid_mode;

	u32 umask = 0;

	int ret;
@@ -1618,12 +1647,19 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	if (mask & ~valid_mask)

		return -EINVAL;





	/* We don't allow FAN_MARK_IGNORE & FAN_MARK_IGNORED_MASK together */

	if (ignore == (FAN_MARK_IGNORE | FAN_MARK_IGNORED_MASK))

		return -EINVAL;



	/*

	 * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with

	 * FAN_MARK_IGNORED_MASK.

	 */

	if (ignore)

	if (ignore == FAN_MARK_IGNORED_MASK) {

		mask &= ~FANOTIFY_EVENT_FLAGS;

		umask = FANOTIFY_EVENT_FLAGS;

	}



	f = fdget(fanotify_fd);

	if (unlikely(!f.file))
@@ -1727,6 +1763,13 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	else

		mnt = path.mnt;



	ret = mnt ? -EINVAL : -EISDIR;

	/* FAN_MARK_IGNORE requires SURV_MODIFY for sb/mount/dir marks */

	if (mark_cmd == FAN_MARK_ADD && ignore == FAN_MARK_IGNORE &&

	    (mnt || S_ISDIR(inode->i_mode)) &&

	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY))

		goto path_put_and_out;



	/* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */

	if (mnt || !S_ISDIR(inode->i_mode)) {

		mask &= ~FAN_EVENT_ON_CHILD;
@@ -1819,7 +1862,7 @@ static int __init fanotify_user_setup(void) 


	BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 12);

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 10);

	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);



	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,

					 SLAB_PANIC|SLAB_ACCOUNT);

include/linux/fanotify.h

+4 −1
Original line number Diff line number Diff line
@@ -62,11 +62,14 @@ 
#define FANOTIFY_MARK_CMD_BITS	(FAN_MARK_ADD | FAN_MARK_REMOVE | \

				 FAN_MARK_FLUSH)



#define FANOTIFY_MARK_IGNORE_BITS (FAN_MARK_IGNORED_MASK | \

				   FAN_MARK_IGNORE)



#define FANOTIFY_MARK_FLAGS	(FANOTIFY_MARK_TYPE_BITS | \

				 FANOTIFY_MARK_CMD_BITS | \

				 FANOTIFY_MARK_IGNORE_BITS | \

				 FAN_MARK_DONT_FOLLOW | \

				 FAN_MARK_ONLYDIR | \

				 FAN_MARK_IGNORED_MASK | \

				 FAN_MARK_IGNORED_SURV_MODIFY | \

				 FAN_MARK_EVICTABLE)

include/uapi/linux/fanotify.h

+8 −0
Original line number Diff line number Diff line
@@ -83,12 +83,20 @@ 
#define FAN_MARK_FLUSH		0x00000080

/* FAN_MARK_FILESYSTEM is	0x00000100 */

#define FAN_MARK_EVICTABLE	0x00000200

/* This bit is mutually exclusive with FAN_MARK_IGNORED_MASK bit */

#define FAN_MARK_IGNORE		0x00000400



/* These are NOT bitwise flags.  Both bits can be used togther.  */

#define FAN_MARK_INODE		0x00000000

#define FAN_MARK_MOUNT		0x00000010

#define FAN_MARK_FILESYSTEM	0x00000100



/*

 * Convenience macro - FAN_MARK_IGNORE requires FAN_MARK_IGNORED_SURV_MODIFY

 * for non-inode mark types.

 */

#define FAN_MARK_IGNORE_SURV	(FAN_MARK_IGNORE | FAN_MARK_IGNORED_SURV_MODIFY)



/* Deprecated - do not use this in programs and do not add new flags here! */

#define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\

				 FAN_MARK_REMOVE |\