oss-security - Re: CVE request - kernel: information leak in sigaltstack

Openwall GNU/*/Linux 3.0 - a small security-enhanced Linux distro for servers

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Date: Wed, 05 Aug 2009 10:05:55 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: "Steven M. Christey" <coley@...us.mitre.org>, jon@...rheide.org
Subject: Re: CVE request - kernel: information leak in sigaltstack

Eugene Teo wrote:
> do_sigaltstack: avoid copying 'stack_t' as a structure to user space
> 
> Ulrich Drepper correctly points out that there is generally padding in
> the structure on 64-bit hosts, and that copying the structure from
> kernel to user space can leak information from the kernel stack in those
> padding bytes.
> 
> Avoid the whole issue by just copying the three members one by one
> instead, which also means that the function also can avoid the need for
> a stack frame. This also happens to match how we copy the new structure
> from user space, so it all even makes sense.
> 
> Upstream commit:
> http://git.kernel.org/linus/0083fc2c50e6c5127c2802ad323adf8143ab7856
> 
> Reference:
> https://bugzilla.redhat.com/show_bug.cgi?id=515392

Reproducer:
http://milw0rm.com/exploits/9352

Thanks, Eugene

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