Commit 6f8ff537 authored Oct 26, 2011 by Curt Wohlgemuth Committed by Theodore Ts'o Oct 26, 2011

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>

parent f85b287a

fs/ext4/extents.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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 {