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SubjectRe: brk randomization breaks columns
Hi!

> Still, it will probably not fix your particular program crashes, just
> because it will always assume that brk starts immediately after the end of
> the bss, which is plain wrong and has never been assured. Could you please
> check whether there is any compat-* package available for you
> distribution, that upgrades libc.so.5 to any fixed version?

I got libc.so.5 as a binary from some Slackware-based system, IIRC,
and I can't find any relevant compat-* packages :-(.

> From: Jiri Kosina <jkosina@suse.cz>
>
> brk: check the lower bound properly
>
> There is a check in sys_brk(), that tries to make sure that we do not
> underflow the area that is dedicated to brk heap.
>
> The check is however wrong, as it assumes that brk area starts immediately
> after the end of the code (+bss), which is wrong for example in
> environments with randomized brk start. The proper way is to check whether
> the address is not below the start_brk address.
>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>

ACK.


> diff --git a/mm/mmap.c b/mm/mmap.c
> index 8295577..1c3b48f 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -241,7 +241,7 @@ asmlinkage unsigned long sys_brk(unsigned long brk)
>
> down_write(&mm->mmap_sem);
>
> - if (brk < mm->end_code)
> + if (brk < mm->start_brk)
> goto out;
>
> /*

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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