Merge tag 'for-5.14-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fix from David Sterba:
 "One more fix for cross-rename, adding a missing check for directory
  and subvolume, this could lead to a crash"

* tag 'for-5.14-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: prevent rename2 from exchanging a subvol with a directory from different parents

Author: torvalds

fs/btrfs/inode.c

@@ -9226,8 +9226,14 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 	bool dest_log_pinned = false;
 	bool need_abort = false;
 
-	/* we only allow rename subvolume link between subvolumes */
-	if (old_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest)
+	/*
+	 * For non-subvolumes allow exchange only within one subvolume, in the
+	 * same inode namespace. Two subvolumes (represented as directory) can
+	 * be exchanged as they're a logical link and have a fixed inode number.
+	 */
+	if (root != dest &&
+	    (old_ino != BTRFS_FIRST_FREE_OBJECTID ||
+	     new_ino != BTRFS_FIRST_FREE_OBJECTID))
 		return -EXDEV;
 
 	/* close the race window with snapshot create/destroy ioctl */