[PATCH v2 1/2] btrfs: Fix superblock csum type check.

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Old csum type check is wrong and can't catch csum_type 1(not supported).

Fix it to avoid hostile 0 division.

Reported-by: Lukas Lueg <lukas.lueg@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
Changelog:
v2:
   Fix existing codes other than adding new one.
---
 fs/btrfs/ctree.h   | 1 +
 fs/btrfs/disk-io.c | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f9c89ca..d6f3aa0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -173,6 +173,7 @@ struct btrfs_ordered_sum;
 
 /* csum types */
 #define BTRFS_CSUM_TYPE_CRC32	0
+#define BTRFS_CSUM_LAST_TYPE	0
 
 static int btrfs_csum_sizes[] = { 4, 0 };
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 639f266..e33a01b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -426,9 +426,9 @@ static int btrfs_check_super_csum(char *raw_disk_sb)
 		}
 	}
 
-	if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
+	if (csum_type > BTRFS_CSUM_LAST_TYPE) {
 		printk(KERN_ERR "BTRFS: unsupported checksum algorithm %u\n",
-				csum_type);
+		       csum_type);
 		ret = 1;
 	}
 
-- 
2.3.5