Patch "fanotify: Split fsid check from other fid mode checks" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fanotify: Split fsid check from other fid mode checks

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fanotify-split-fsid-check-from-other-fid-mode-checks.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a6ca4880d827814fe37a2fc1a6ee669f34e056d3
Author: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Date:   Mon Oct 25 16:27:21 2021 -0300

    fanotify: Split fsid check from other fid mode checks
    
    [ Upstream commit 8299212cbdb01a5867e230e961f82e5c02a6de34 ]
    
    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@xxxxxxxxxxxxx
    Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
    Signed-off-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 20b743b05b997..8cf8e63a2c3e8 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -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;
@@ -1505,7 +1510,11 @@ 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;