[PATCH 4.20 17/50] debugfs: fix debugfs_rename parameter checking

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

commit d88c93f090f708c18195553b352b9f205e65418f upstream.

debugfs_rename() needs to check that the dentries passed into it really
are valid, as sometimes they are not (i.e. if the return value of
another debugfs call is passed into this one.)  So fix this up by
properly checking if the two parent directories are errors (they are
allowed to be NULL), and if the dentry to rename is not NULL or an
error.

Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/debugfs/inode.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -787,6 +787,13 @@ struct dentry *debugfs_rename(struct den
 	struct dentry *dentry = NULL, *trap;
 	struct name_snapshot old_name;
 
+	if (IS_ERR(old_dir))
+		return old_dir;
+	if (IS_ERR(new_dir))
+		return new_dir;
+	if (IS_ERR_OR_NULL(old_dentry))
+		return old_dentry;
+
 	trap = lock_rename(new_dir, old_dir);
 	/* Source or destination directories don't exist? */
 	if (d_really_is_negative(old_dir) || d_really_is_negative(new_dir))