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

[Marius Bakke]

Danny Milosavljevic <address@hidden> 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

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