[grsec] 2.6.10-as2 + grsec 2.1.1 gives userspace segfaults

[pageexec at freemail.hu]

> I've installed 2.6.10-as2 + grsec 2.1.1 on a couple of machines, and all 
> have the same behaviour : With PAX turned on, userspace gives @random 
> segfaults. Coredumps have weird addresses in them.
> 
> Turning off PAX makes it go away. We can rule out hardware problems, all 3
> machines have been rock solid over the years. I'll update the above if I know
> more.

what's your distro/glibc version? also, could you turn off/on the
various randomization options and see which makes the problem go
away (if anything)? thing is, ld.so used to have a bug in its use
of brk() that would cause such issues, but that should have been
worked around in PaX for some time now (you could try to comment
out the brk randomization code in fs/binfmt_elf.c, it's a 1-liner).

with that said, i too saw an 'interesting' crash while compiling
qt and it had all the symptoms of the above mentioned (and supposedly)
fixed bug... so i don't know. what kind of applications crash on
you? would it be possible to acquire a /proc/pid/maps file somehow
at the time of the crash (like, run the app in gdb which will catch
the sigsegv then you can get the maps, or maybe a readelf -l on
the coredump itself, but that has less information)? also, are you
using preempt or 4k stacks or anything 'weird'?