Re: 9.4 beta1 crash on Debian sid/i386

On 2014-05-18 17:41:17 -0400, Tom Lane wrote:
> Christoph Berg <cb(at)df7cb(dot)de> writes:
> > Re: Andres Freund 2014-05-18 <20140518091445(dot)GU23662(at)alap3(dot)anarazel(dot)de>
> >> Did you measure how large the stack actually was when you got the
> >> SIGBUS? Should be possible to determine that by computing the offset
> >> using some local stack variable in one of the depeest stack frames.
>
> > Looking at /proc/*/maps, the stack is ffb38000-ffd1e000 = 1944kB for a
> > process that just got SIGBUS. This seems to be in line with
> > stack_base_ptr = 0xffd1c317 and the fcinfo address in
>
> OK, so the problem is that getrlimit(RLIMIT_STACK) is lying to us about
> the available stack depth. I'd classify that as a kernel bug. I wonder
> if it's a different manifestation of this issue:
> https://bugzilla.redhat.com/show_bug.cgi?id=952946

That'd explain why I couldn't reproduce it. And I seme to recall some
messages about the hardening stuff in debian accidentally being lost
some time ago. So if that got re-introduced into 9.4... The CFLAGS
certainly indicate that -pie is getting used.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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