linux-kernel - Re: [PATCH] swapfile: fix memory corruption via malformed swapfile

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Message-ID: <20161104145704.GB8825@cmpxchg.org>
Date:   Fri, 4 Nov 2016 10:57:04 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Jann Horn <jann@...jh.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Jerome Marchand <jmarchan@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] swapfile: fix memory corruption via malformed swapfile

On Mon, Oct 31, 2016 at 10:32:13PM +0100, Jann Horn wrote:
> When root activates a swap partition whose header has the wrong endianness,
> nr_badpages elements of badpages are swabbed before nr_badpages has been
> checked, leading to a buffer overrun of up to 8GB.
> 
> This normally is not a security issue because it can only be exploited by
> root (more specifically, a process with CAP_SYS_ADMIN or the ability to
> modify a swap file/partition), and such a process can already e.g. modify
> swapped-out memory of any other userspace process on the system.
> 
> Testcase for reproducing the bug (must be run as root, should crash your
> kernel):
[...]
> Cc: stable@...r.kernel.org
> Signed-off-by: Jann Horn <jann@...jh.net>

Acked-by: Johannes Weiner <hannes@...xchg.org>