[PATCH v3] ext4: check for overlapping extents in ext4_valid_extent_entries()

[Theodore Ts'o <tytso@mit.edu>]

On Wed, Oct 23, 2013 at 02:40:30AM +0800, Eryu Guan wrote:
> A corrupted ext4 may have out of order leaf extents, i.e.
> 
> extent: lblk 0--1023, len 1024, pblk 9217, flags: LEAF UNINIT
> extent: lblk 1000--2047, len 1024, pblk 10241, flags: LEAF UNINIT
>              ^^^^ overlap with previous extent
> 
> Reading such extent could hit BUG_ON() in ext4_es_cache_extent().
> 
> 	BUG_ON(end < lblk);
> 
> The problem is that __read_extent_tree_block() tries to cache holes as
> well but assumes 'lblk' is greater than 'prev' and passes underflowed
> length to ext4_es_cache_extent(). Fix it by checking for overlapping
> extents in ext4_valid_extent_entries().
> 
> I hit this when fuzz testing ext4, and am able to reproduce it by
> modifying the on-disk extent by hand.
> 
> Also add the check for (ee_block + len - 1) in ext4_valid_extent() to
> make sure the value is not overflow.
> 
> Ran xfstests on patched ext4 and no regression.
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Lukáš Czerner <lczerner@redhat.com>
> Signed-off-by: Eryu Guan <guaneryu@gmail.com>

Thanks, applied.

						- Ted
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