From bfae7d5cd2bef44fcc95f34c72d6843f91fa49c9 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: Thu, 26 Jan 2017 11:50:00 +0200
Subject: [PATCH] ext4/fscrypto: avoid RCU lookup in d_revalidate

As Al pointed, d_revalidate should return RCU lookup before using d_inode.
This was originally introduced by:
commit 34286d666230 ("fs: rcu-walk aware d_revalidate method").

Change-Id: I81999f7b4651d7dd64695c94d15561dfdcec851b
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: stable <stable@vger.kernel.org>
Git-commit: 03a8bb0e53d9562276045bdfcf2b5de2e4cff5a1
Git-repo: git://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git
[andreym@codeaurora.org: resolve merge conflicts,
 fs/crypto/crypto.c does not exist in current branch,
 had to omit it]
Signed-off-by: Andrey Markovytch <andreym@codeaurora.org>
---
 fs/ext4/crypto.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index 1bb67391225a..664f42c850b7 100644
--- a/fs/ext4/crypto.c
+++ b/fs/ext4/crypto.c
@@ -34,6 +34,7 @@
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/spinlock_types.h>
+#include <linux/namei.h>
 
 #include "ext4_extents.h"
 #include "xattr.h"
@@ -487,6 +488,9 @@ static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
 	struct ext4_crypt_info *ci;
 	int dir_has_key, cached_with_key;
 
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
 	dir = dget_parent(dentry);
 	if (!ext4_encrypted_inode(d_inode(dir))) {
 		dput(dir);