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Message-ID: <47D03440.6090503@gnu.org>
Date: Thu, 06 Mar 2008 19:13:20 +0100
From: Paolo Bonzini <bonzini@....org>
To: Olivier Galibert <galibert@...ox.com>,
Joe Buck <Joe.Buck@...opsys.COM>,
Paolo Bonzini <bonzini@....org>,
"H. Peter Anvin" <hpa@...or.com>,
Chris Lattner <clattner@...le.com>,
Michael Matz <matz@...e.de>,
Richard Guenther <richard.guenther@...il.com>,
Jan Hubicka <hubicka@....cz>,
Aurelien Jarno <aurelien@...el32.net>,
linux-kernel@...r.kernel.org, gcc@....gnu.org
Subject: Re: RELEASE BLOCKER: Linux doesn't follow x86/x86-64 ABI wrt direction
flag
Olivier Galibert wrote:
> On Thu, Mar 06, 2008 at 09:58:41AM -0800, Joe Buck wrote:
>> If the kernel allows state to leak from one process to another,
>> for example from a process running as root to a process running as an
>> ordinary user, it's a bug, with possible security implications.
>
> I don't think that it is relevant in your case. If you have the
> signal handler in something that does not share the VM with the
> interrupted thread, you will have a context switch which is supposed
> to store the direction flag and restore the one from the handling
> thread. If you share the VM there is no context switch but you have
> access to the exact same memory with the exact same rights, making the
> leak irrelevant.
A process can send a signal via kill. IOW, a malicious process can
*control when the process would be interrupted* in order to get it into
the signal handler with DF=1.
Paolo
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