linux-ext4 - Re: [PATCH 1/1] ext4: fix potential negative array index in do

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Message-ID: <20200730014835.GC44720@mit.edu>
Date:   Wed, 29 Jul 2020 21:48:35 -0400
From:   tytso@....edu
To:     Eric Sandeen <sandeen@...hat.com>
Cc:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/1] ext4: fix potential negative array index in
 do_split()

On Wed, Jun 17, 2020 at 02:19:04PM -0500, Eric Sandeen wrote:
> If for any reason a directory passed to do_split() does not have enough
> active entries to exceed half the size of the block, we can end up
> iterating over all "count" entries without finding a split point.
> 
> In this case, count == move, and split will be zero, and we will
> attempt a negative index into map[].
> 
> Guard against this by detecting this case, and falling back to
> split-to-half-of-count instead; in this case we will still have
> plenty of space (> half blocksize) in each split block.
> 
> Fixes: ef2b02d3e617 ("ext34: ensure do_split leaves enough free space in both blocks")
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>

Thanks, applied.

						- Ted