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Date: Tue, 20 Feb 2018 13:29:02 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: kernel-hardening@...ts.openwall.com, Kees Cook <keescook@...omium.org>,
 PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>,
 Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
 Tycho Andersen <tycho@...ho.ws>, Laura Abbott <labbott@...hat.com>,
 Mark Rutland <mark.rutland@....com>,
 Ard Biesheuvel <ard.biesheuvel@...aro.org>, Borislav Petkov <bp@...en8.de>,
 Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>,
 Peter Zijlstra <a.p.zijlstra@...llo.nl>, "Dmitry V . Levin"
 <ldv@...linux.org>, x86@...nel.org, Mohamed Ghannam <simo.ghannam@...il.com>
Subject: Re: [PATCH RFC v8 0/6] Introduce the STACKLEAK feature and a test for
 it

On 16.02.2018 21:10, Alexander Popov wrote:
> This is the 8th version of the patch series introducing STACKLEAK to the
> mainline kernel. I've made some minor improvements while waiting for the
> next review by x86 maintainers.
> 
> STACKLEAK is a security feature developed by Grsecurity/PaX (kudos to them),
> which:
>  - reduces the information that can be revealed through kernel stack leak bugs;
>  - blocks some uninitialized stack variable attacks (e.g. CVE-2010-2963);
>  - introduces some runtime checks for kernel stack overflow detection.

Hello! I've just tested STACKLEAK against the recent CVE-2017-17712 exploit:
http://openwall.com/lists/oss-security/2018/02/20/1

This vulnerability is a race condition in raw_sendmsg() in net/ipv4/raw.c. It
leads to uninitialized stack pointer usage which can be used for a local
privilege escalation.

CVE-2017-17712 was discovered and fixed by Mohamed Ghannam (kudos to him!). He
also provided a stable PoC exploit for it.

With STACKLEAK, the uninitialized stack pointer is set to STACKLEAK_POISON
(-0xBEEF) and points to the unused hole in the virtual memory map. That blocks
the stack spraying needed for CVE-2017-17712 exploit (similar to CVE-2010-2963).

Best regards,
Alexander

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