Subject: Re: bug#27429: Stack clash (CVE-2017-1000366 etc); -fstack-check

From: Leo Famulari <[email-masked]>
Date: Sun, 25 Jun 2017 09:19:45 -0400

I agree, let's wait for guidance from the upstream GCC and GLIBC developers.

-------- Original Message --------
From: Marius Bakke <[email-masked]>
Sent: June 25, 2017 6:41:06 AM EDT
To: Danny Milosavljevic <[email-masked]>, [email-masked]
Subject: bug#27429: Stack clash (CVE-2017-1000366 etc); -fstack-check

Danny Milosavljevic <[email-masked]> writes:

> Hi,
>
> what do you all think of rebuilding the world with "-fstack-check" (either now or later on) ?
>
> That would make gcc emit code to always grow the stack in a way that it certainly touches each 4 KiB (parametrizable by STACK_CHECK_PROBE_INTERVAL_EXP) page on the way.
>
> I think that would be the right and permanent fix - unlike the whack-a-mole approach where we patch programs not to do what they are supposed to do, if their stack allocation happens to grow.
>
> See also <https://www.qualys.com/2017/06/19/stack-clash/stack-clash.txt> and <https://gcc.gnu.org/onlinedocs/gccint/Stack-Checking.html>.

Red Hat investigated this during the embargo[0] and found that the
current implementation in GCC has problems[1]. We should wait until
those issues are resolved first, but sounds good to me.

[0] http://seclists.org/oss-sec/2017/q2/556
[1] http://seclists.org/oss-sec/2017/q2/505