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Date: Tue, 20 Feb 2018 13:29:02 +0300
From: Alexander Popov <>
To:, Kees Cook <>,
 PaX Team <>, Brad Spengler <>,
 Ingo Molnar <>, Andy Lutomirski <>,
 Tycho Andersen <>, Laura Abbott <>,
 Mark Rutland <>,
 Ard Biesheuvel <>, Borislav Petkov <>,
 Thomas Gleixner <>, "H . Peter Anvin" <>,
 Peter Zijlstra <>, "Dmitry V . Levin"
 <>,, Mohamed Ghannam <>
Subject: Re: [PATCH RFC v8 0/6] Introduce the STACKLEAK feature and a test for

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:

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,

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