linux-ext4 - Re: [PATCH] ext4: prevent right-shifting extents beyond EXT_MAX

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Date:   Thu, 12 Apr 2018 11:53:04 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     linux-ext4@...r.kernel.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] ext4: prevent right-shifting extents beyond
 EXT_MAX_BLOCKS

On Tue, Apr 10, 2018 at 12:01:04AM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> During the "insert range" fallocate operation, extents starting at the
> range offset are shifted "right" (to a higher file offset) by the range
> length.  But, as shown by syzbot, it's not validated that this doesn't
> cause extents to be shifted beyond EXT_MAX_BLOCKS.  In that case
> ->ee_block can wrap around, corrupting the extent tree.
> 
> Fix it by returning an error if the space between the end of the last
> extent and EXT4_MAX_BLOCKS is smaller than the range being inserted.
> 

Applied, thanks.

						- Ted