Date:	Mon, 27 Jul 2015 15:03:12 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Sebastian Parschauer <s.parschauer@....de>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stable Kernel <stable@...r.kernel.org>,
	Michael Davidson <md@...gle.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jiri Kosina <jkosina@...e.cz>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Ubuntu Kernel Team <kernel-team@...ts.ubuntu.com>
Subject: Stable backport of ASLR fixes?

Hi Greg,

Have you had a chance to look at this? I think we need to either
include the ASLR improvements in stable or revert
a87938b2e246b81b4fb713edb371a9fa3c5c3c86, which breaks existing
userspace tools.

-Kees

On Thu, Jul 16, 2015 at 1:34 PM, Kees Cook <keescook@...omium.org> wrote:
> On Thu, Jul 16, 2015 at 12:57 PM, Sebastian Parschauer
> <s.parschauer@....de> wrote:
>> I'm a professional Linux game cheater and the co-maintainer of scanmem.
>> With scanmem we determine the load addresses for PIC and PIE binaries to
>> be able to support static memory cheating with ASLR. At the moment
>> ugtrain is the only universal game trainer able to determine the PIE
>> load address as well and to re-add it to the found match offset from
>> scanmem.
>
> scanmem is such a fun tool. :)
>
>> I'd like to complain a bit about this patch as it makes the address
>> space layout for the executable really ugly by loading unrelated stuff
>> between .text and .rodata.
>>
>> Is it really required on top of 3.13 or 3.16 where Ubuntu has put it?
>>
>> I've also checked v4.2-rc1. There everything is beautiful again.
>> Thank you very much for that!
>>
>> References:
>> https://github.com/scanmem/scanmem/issues/122
>> https://github.com/ugtrain/ugtrain
>
> To summarize the two commits:
>
> This commit fixed a problem where PIE binaries could collide with
> other memory regions, but breaks scanmem:
> https://git.kernel.org/linus/a87938b2e246b81b4fb713edb371a9fa3c5c3c86
> It was sent to stable (and various distros like Ubuntu picked it up),
> since it was (correctly) seen as a bug fix (without realizing it broke
> other programs).
>
> This commit reorganized PIE ASLR to split it from mmap ASLR:
> https://git.kernel.org/linus/a87938b2e246b81b4fb713edb371a9fa3c5c3c86
> This was part of a larger series of patches that did refactoring
> across multiple architectures, and was not sent to stable (since it is
> considered more of a feature than a bug fix).
>
> I believe it should be safe to backport the series, but not every
> kernel team will be willing to do that on their own. As the series has
> been living fine since 4.1, I could be convinced that it should be
> sent to stable. It does fix an ASLR weakness, and it does fix a
> situation where the other commit that got sent to stable breaks
> existing userspace tools. I think both of those factors together
> warrants sending the series to stable.
>
> Greg, would you be willing to take these into stable?
>
> fbbc400f3924ce095b466c776dc294727ec0a202
> 82168140bc4cec7ec9bad39705518541149ff8b7
> dd04cff1dceab18226853b555cf07914648a235f
> 1f0569df0b0285e7ec2432d804a4921b06a61618
> ed6322746afb74c2509e2f3a6464182793b16eb9
> 8e89a356feb6f196824a72101861d931a97ac2d2
> 2b68f6caeac271620cd2f9362aeaed360e317df0
> c6f5b001e65cdac592b65a08c5d2dd179cfba568
> d1fd836dcf00d2028c700c7e44d2c23404062c90
> 204db6ed17743000691d930368a5abd6ea541c58
>
> Thanks!
>
> -Kees
>
> --
> Kees Cook
> Chrome OS Security



-- 
Kees Cook
Chrome OS Security
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