Date: Fri, 4 Nov 2016 10:57:04 -0400
From: Johannes Weiner <hannes@cmpxchg.org>
To: Jann Horn <jann@thejh.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Jerome Marchand <jmarchan@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] swapfile: fix memory corruption via malformed swapfile
Message-ID: <20161104145704.GB8825@cmpxchg.org>
References: <1477949533-2509-1-git-send-email-jann@thejh.net>
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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@vger.kernel.org
> Signed-off-by: Jann Horn <jann@thejh.net>

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