Re: brk randomization breaks columns

From: Jiri Kosina
Date: Mon Feb 04 2008 - 09:34:29 EST


On Mon, 4 Feb 2008, Ingo Molnar wrote:

> hm, so it seems that it isnt even the randomization that causes the
> problem - but somehow the randomization code itself is broken, right?
> Would you be interested in figuring out how to unbreak this? [if not,
> could you send me the binary?]

I still don't seem to fully understand what is happening here -- aparently
this is triggerable only with old programs linked against libc.so.5, and I
am not able to trigger it with my trivial program when I link it against
old libc.so.5, which just basically does brk() and checks whether
/proc/<pid>/maps are OK. Seems to me that (at least certain versions) of
libc.so.5 (wrongly) assume that end of the bss is the start of the heap,
but I will try to investigate it more.

Ingo, the code in commit c1d171a0029 is IMHO funcionalli identical to
your exec-shield in fedora kernels, so even libc.so.5-linked binaries on
any Fedora distro should trigger this bug ... (or you can use the binary
that Pavel supplied). Haven't tried this yet.

Thanks,

--
Jiri Kosina
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