linux-kernel - [PATCH 4.4 18/20] ext4/fscrypto: avoid RCU lookup in d

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Date:   Fri,  5 May 2017 11:33:08 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Theodore Tso <tytso@....edu>,
        Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH 4.4 18/20] ext4/fscrypto: avoid RCU lookup in d_revalidate

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

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

From: Jaegeuk Kim <jaegeuk@...nel.org>

commit 03a8bb0e53d9562276045bdfcf2b5de2e4cff5a1 upstream.

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").

Reported-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: Theodore Ts'o <tytso@....edu>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ext4/crypto.c |    4 ++++
 1 file changed, 4 insertions(+)

--- 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"
@@ -481,6 +482,9 @@ static int ext4_d_revalidate(struct dent
 	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);