Commit 8299212c authored by Gabriel Krisman Bertazi's avatar Gabriel Krisman Bertazi Committed by Jan Kara
Browse files

fanotify: Split fsid check from other fid mode checks 

FAN_FS_ERROR will require fsid, but not necessarily require the
filesystem to expose a file handle.  Split those checks into different
functions, so they can be used separately when setting up an event.

While there, update a comment about tmpfs having 0 fsid, which is no
longer true.

Link: https://lore.kernel.org/r/20211025192746.66445-7-krisman@collabora.com


Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent b9928e80

fs/notify/fanotify/fanotify_user.c

+18 −9
Original line number Diff line number Diff line
@@ -1300,16 +1300,15 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) 
	return fd;

}



/* Check if filesystem can encode a unique fid */

static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)

static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)

{

	__kernel_fsid_t root_fsid;

	int err;



	/*

	 * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).

	 * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).

	 */

	err = vfs_get_fsid(path->dentry, fsid);

	err = vfs_get_fsid(dentry, fsid);

	if (err)

		return err;
@@ -1317,10 +1316,10 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) 
		return -ENODEV;



	/*

	 * Make sure path is not inside a filesystem subvolume (e.g. btrfs)

	 * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)

	 * which uses a different fsid than sb root.

	 */

	err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);

	err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);

	if (err)

		return err;
@@ -1328,6 +1327,12 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) 
	    root_fsid.val[1] != fsid->val[1])

		return -EXDEV;



	return 0;

}



/* Check if filesystem can encode a unique fid */

static int fanotify_test_fid(struct dentry *dentry)

{

	/*

	 * We need to make sure that the file system supports at least

	 * encoding a file handle so user can use name_to_handle_at() to
@@ -1335,8 +1340,8 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) 
	 * objects. However, name_to_handle_at() requires that the

	 * filesystem also supports decoding file handles.

	 */

	if (!path->dentry->d_sb->s_export_op ||

	    !path->dentry->d_sb->s_export_op->fh_to_dentry)

	if (!dentry->d_sb->s_export_op ||

	    !dentry->d_sb->s_export_op->fh_to_dentry)

		return -EOPNOTSUPP;



	return 0;
@@ -1487,7 +1492,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
	}



	if (fid_mode) {

		ret = fanotify_test_fid(&path, &__fsid);

		ret = fanotify_test_fsid(path.dentry, &__fsid);

		if (ret)

			goto path_put_and_out;



		ret = fanotify_test_fid(path.dentry);

		if (ret)

			goto path_put_and_out;