From 6f8ff537266ee5396c920fb0c842a21df3055ff3 Mon Sep 17 00:00:00 2001 From: Curt Wohlgemuth 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 Signed-off-by: "Theodore Ts'o" --- 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 02a4d80573a1..797b63b59740 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 { -- 2.20.1