Commit 8698e3ba authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fanotify: refine the validation checks on non-dir inode mask 

Commit ceaf69f8 ("fanotify: do not allow setting dirent events in
mask of non-dir") added restrictions about setting dirent events in the
mask of a non-dir inode mark, which does not make any sense.

For backward compatibility, these restictions were added only to new
(v5.17+) APIs.

It also does not make any sense to set the flags FAN_EVENT_ON_CHILD or
FAN_ONDIR in the mask of a non-dir inode.  Add these flags to the
dir-only restriction of the new APIs as well.

Move the check of the dir-only flags for new APIs into the helper
fanotify_events_supported(), which is only called for FAN_MARK_ADD,
because there is no need to error on an attempt to remove the dir-only
flags from non-dir inode.

Fixes: ceaf69f8 ("fanotify: do not allow setting dirent events in mask of non-dir")
Link: https://lore.kernel.org/linux-fsdevel/20220627113224.kr2725conevh53u4@quack3.lan/
Link: https://lore.kernel.org/r/20220627174719.2838175-1-amir73il@gmail.com


Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent ca1fdab7

fs/notify/fanotify/fanotify_user.c

+19 −15
Original line number Diff line number Diff line
@@ -1513,8 +1513,15 @@ static int fanotify_test_fid(struct dentry *dentry) 
	return 0;

}



static int fanotify_events_supported(struct path *path, __u64 mask)

static int fanotify_events_supported(struct fsnotify_group *group,

				     struct path *path, __u64 mask,

				     unsigned int flags)

{

	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);



	/*

	 * Some filesystems such as 'proc' acquire unusual locks when opening

	 * files. For them fanotify permission events have high chances of
@@ -1526,6 +1533,16 @@ static int fanotify_events_supported(struct path *path, __u64 mask) 
	if (mask & FANOTIFY_PERM_EVENTS &&

	    path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)

		return -EINVAL;



	/*

	 * We shouldn't have allowed setting dirent events and the directory

	 * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,

	 * but because we always allowed it, error only when using new APIs.

	 */

	if (strict_dir_events && mark_type == FAN_MARK_INODE &&

	    !d_is_dir(path->dentry) && (mask & FANOTIFY_DIRONLY_EVENT_BITS))

		return -ENOTDIR;



	return 0;

}
@@ -1672,7 +1689,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
		goto fput_and_out;



	if (flags & FAN_MARK_ADD) {

		ret = fanotify_events_supported(&path, mask);

		ret = fanotify_events_supported(group, &path, mask, flags);

		if (ret)

			goto path_put_and_out;

	}
@@ -1695,19 +1712,6 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	else

		mnt = path.mnt;



	/*

	 * FAN_RENAME is not allowed on non-dir (for now).

	 * We shouldn't have allowed setting any dirent events in mask of

	 * non-dir, but because we always allowed it, error only if group

	 * was initialized with the new flag FAN_REPORT_TARGET_FID.

	 */

	ret = -ENOTDIR;

	if (inode && !S_ISDIR(inode->i_mode) &&

	    ((mask & FAN_RENAME) ||

	     ((mask & FANOTIFY_DIRENT_EVENTS) &&

	      FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID))))

		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;

include/linux/fanotify.h

+4 −0
Original line number Diff line number Diff line
@@ -111,6 +111,10 @@ 
					 FANOTIFY_PERM_EVENTS | \

					 FAN_Q_OVERFLOW | FAN_ONDIR)



/* Events and flags relevant only for directories */

#define FANOTIFY_DIRONLY_EVENT_BITS	(FANOTIFY_DIRENT_EVENTS | \

					 FAN_EVENT_ON_CHILD | FAN_ONDIR)



#define ALL_FANOTIFY_EVENT_BITS		(FANOTIFY_OUTGOING_EVENTS | \

					 FANOTIFY_EVENT_FLAGS)