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@xxxxxxxxxx> --- fs/ext4/extents.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 57cf568..063a5b8 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1395,7 +1395,9 @@ ext4_ext_next_allocated_block(struct ext4_ext_path *path) while (depth >= 0) { if (depth == path->p_depth) { /* leaf */ - if (path[depth].p_ext != + /* p_ext can be NULL */ + 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 { -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html