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>
---
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