From 6f8ff537266ee5396c920fb0c842a21df3055ff3 Mon Sep 17 00:00:00 2001
From: Curt Wohlgemuth <curtw@google.com>
Date: Wed, 26 Oct 2011 04:38:59 -0400
Subject: [PATCH] ext4: handle NULL p_ext in ext4_ext_next_allocated_block()
In ext4_ext_next_allocated_block(), the path[depth] might
have a p_ext that is NULL -- see ext4_ext_binsearch(). In
such a case, dereferencing it will crash the machine.
This patch checks for p_ext == NULL in
ext4_ext_next_allocated_block() before dereferencinging it.
Tested using a hand-crafted an inode with eh_entries == 0 in
an extent block, verified that running FIEMAP on it crashes
without this patch, works fine with it.
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/extents.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 02a4d80573a18..797b63b597400 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1392,7 +1392,8 @@ ext4_ext_next_allocated_block(struct ext4_ext_path *path)
while (depth >= 0) {
if (depth == path->p_depth) {
/* leaf */
- if (path[depth].p_ext !=
+ if (path[depth].p_ext &&
+ path[depth].p_ext !=
EXT_LAST_EXTENT(path[depth].p_hdr))
return le32_to_cpu(path[depth].p_ext[1].ee_block);
} else {
--
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