Re: 9.4 beta1 crash on Debian sid/i386

On 2014-05-18 11:08:34 +0200, Christoph Berg wrote:
> > > Interestingly, the Debian buildd managed to run the testsuite for
> > > i386, while I could reproduce the problem on the pgapt build machine
> > > and on my notebook, so there must be some system difference. Possibly
> > > the reason is these two machines are running a 64bit kernel and I'm
> > > building in a 32bit chroot, though that hasn't been a problem before.
> >
> > I'm suspicious that something has changed in your build environment,
> > because that stack-checking logic hasn't changed since these commits:
>
> It's something in the combination of build and runtime environment. I
> can reproduce the problem in the package that the Debian
> i386/experimental buildd has compiled, including passing the
> regression tests there. Possibly a change in libc there. I'll try to
> ask some kernel/libc people if they have an idea. My current bet is on
> the gcc hardening flags we are using.

As another datapoint: I don't see the problem on 32bit packages build
with a 64bit gcc with -m32 on debian unstable on my laptop. Didn't try
hard though.

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.

Greetings,

Andres Freund