Re: 9.4 beta1 crash on Debian sid/i386

On 2014-05-18 23:52:32 +0200, Andres Freund wrote:
> On 2014-05-18 17:41:17 -0400, Tom Lane wrote:
> > Christoph Berg <cb@df7cb.de> writes:
> > > Re: Andres Freund 2014-05-18 <20140518091445.GU23662@alap3.anarazel.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.

Indeed. If I add -pie to my 32bit vpath's configure invocation it
crashes, too. Not that that helps much to resolve the bug, given it's
been sedentary for a long while :(.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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