From: Roel Kluin <roel.kluin@gmail.com>
Date: Tue, 26 Jul 2011 10:14:43 +0000 (+1000)
Subject: Don't dereference em if it's NULL or an error pointer.
X-Git-Tag: next-20110802~1^2~54
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4198a5ac91fb10c60c47d7f6d32f49ba9b45f43b;p=karo-tx-linux.git

Don't dereference em if it's NULL or an error pointer.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ae762dab37f8..4c4c4af7ccbc 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1865,7 +1865,8 @@ static int btrfs_io_failed_hook(struct bio *failed_bio,
 
 		read_lock(&em_tree->lock);
 		em = lookup_extent_mapping(em_tree, start, failrec->len);
-		if (em->start > start || em->start + em->len < start) {
+		if (em && !IS_ERR(em) && (em->start > start ||
+					em->start + em->len < start)) {
 			free_extent_map(em);
 			em = NULL;
 		}