From: Dan Carpenter <error27@gmail.com>
Date: Tue, 10 Nov 2009 09:01:43 +0000 (+0000)
Subject: Btrfs: avoid null deref in unpin_extent_cache()
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=4eb3991c5def39bcf553c14ebe2618fcb47b627f;p=openwrt%2Fstaging%2Fblogic.git

Btrfs: avoid null deref in unpin_extent_cache()

I re-orderred the checks to avoid dereferencing "em" if it was null.

Found by smatch static checker.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
---

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 2c726b7b9faa..ccbdcb54ec5d 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -208,7 +208,7 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
 	write_lock(&tree->lock);
 	em = lookup_extent_mapping(tree, start, len);
 
-	WARN_ON(em->start != start || !em);
+	WARN_ON(!em || em->start != start);
 
 	if (!em)
 		goto out;