linux-kernel - Re: [PATCH v2] all arches, signal: Move restart_block to struct task

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Date:	Mon, 10 Nov 2014 21:13:19 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	luto@...capital.net
Cc:	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, linux-arch@...r.kernel.org,
	viro@...iv.linux.org.uk, richard.weinberger@...il.com,
	hpa@...or.com, mingo@...nel.org, keescook@...omium.org
Subject: Re: [PATCH v2] all arches, signal: Move restart_block to struct
 task_struct

From: Andy Lutomirski <luto@...capital.net>
Date: Mon, 10 Nov 2014 14:03:23 -0800

> On Wed, Oct 29, 2014 at 11:12 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>> On Wed, 29 Oct 2014, Andy Lutomirski wrote:
>>
>>> If an attacker can cause a controlled kernel stack overflow,
>>> overwriting the restart block is a very juicy exploit target.
>>> Moving the restart block to struct task_struct prevents this
>>> exploit.
>>>
>>> Note that there are other fields in thread_info that are also easy
>>> targets, at least on some architectures.
>>>
>>> It's also a decent simplification, since the restart code is more or
>>> less identical on all architectures.
>>
>> I think that's the most important change. Moving common stuff into
>> common code. The side effect of slightly reducing the attack surface
>> is nice, but as Al pointed out not really the big win here.
> 
> Having gotten exactly zero feedback from any arch maintainer outside
> of x86, am I supposed to pester people further?

No objections wrt. sparc and if things break I'll help fix it.
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