From d88c93f090f708c18195553b352b9f205e65418f Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 23 Jan 2019 11:27:02 +0100
Subject: [PATCH] debugfs: fix debugfs_rename parameter checking

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@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/debugfs/inode.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 13b01351dd1cb..41ef452c1fcfb 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -787,6 +787,13 @@ struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
 	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))
-- 
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