Date: Sun, 20 Aug 2006 21:16:29 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Solar Designer <solar@openwall.com>
Cc: Willy Tarreau <wtarreau@hera.kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] introduce CONFIG_BINFMT_ELF_AOUT
Message-ID: <20060821001628.GC2861@dmt>
References: <20060819232556.GA16617@openwall.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20060819232556.GA16617@openwall.com>
User-Agent: Mutt/1.4.2.1i
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1760
Lines: 39

On Sun, Aug 20, 2006 at 03:25:56AM +0400, Solar Designer wrote:
> Willy,
> 
> I propose the attached patch (extracted from 2.4.33-ow1) for inclusion
> into 2.4.34-pre.  (2.6 kernels could benefit from the same change, too.)
> 
> The patch adds a new compile-time option to control the support for
> "ELF binaries with a.out format interpreters or a.out libraries".
> Without this patch, such support is enabled on every system that enables
> the support for ELF binaries - although 99% (100%?) of systems don't
> need this hybrid functionality.  Moreover, this functionality poses a
> security risk - as proven in practice:
> 
> 	http://www.isec.pl/vulnerabilities/isec-0021-uselib.txt
> 
> This uselib() vulnerability did not affect default kernel builds with
> the -ow patch specifically due to separation of the unneeded/risky code
> into CONFIG_BINFMT_ELF_AOUT and having this option disabled by default.
> (Yes, this change in -ow patches pre-dates the discovery of the uselib()
> vulnerability.)
> 
> The patch also changes CONFIG_BINFMT_AOUT to be disabled by default on
> archs that had it default to enabled.  The a.out support is similarly
> risky and not audited/hardened with the same scrutiny that the ELF
> support has received.

I dislike this change. "Make a.out configurable" is a:

- "Hide the problems" trick, making it less likely for any potential bug to
be really fixed.

- Change not suitable for v2.4 inclusion: its not fixing _any_ serious problem.

We had this discussion before, didnt we?
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/