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

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Date:	Mon, 1 Dec 2014 06:55:01 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Richard Weinberger <richard@....at>
Cc:	David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2] all arches, signal: Move restart_block to struct task_struct

On Tue, Nov 11, 2014 at 2:52 AM, Richard Weinberger <richard@....at> wrote:
> Am 11.11.2014 um 03:13 schrieb David Miller:
>> 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.
>
> Same for UML.
> Acked-by: Richard Weinberger <richard@....at>

akpm, do you consider this appropriate for either 3.19 or 3.20?  If
so, can you add it to the appropriate part of -mm?

Thanks,
Andy
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