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From: Pavel Machek <pavel@ucw.cz>
To: Jiri Kosina <jkosina@suse.cz>
Cc: kernel list <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@elte.hu>,
	Abel Bernabeu <abel.bernabeu@gmail.com>,
	Hugh Dickins <hugh@veritas.com>,
	Arjan van de Ven <arjan@infradead.org>
Subject: Re: brk randomization breaks columns
Date: Tue, 5 Feb 2008 17:02:14 +0100	[thread overview]
Message-ID: <20080205160214.GD24331@elf.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.64.0802050242440.30873@twin.jikos.cz>

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

  parent reply	other threads:[~2008-02-05 16:03 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 12:28 Pavel Machek
2008-02-04 13:01 ` Ingo Molnar
2008-02-04 13:28   ` Pavel Machek
2008-02-04 14:55     ` Jiri Kosina
2008-02-04 20:25       ` Pavel Machek
2008-02-04 14:33   ` Jiri Kosina
2008-02-04 16:12     ` Jiri Kosina
     [not found]       ` <15577be70802041016m97cddbfk43b9073408bcbce9@mail.gmail.com>
     [not found]         ` <15577be70802041029o2975ba6do34589bbdc81d1652@mail.gmail.com>
2008-02-04 19:52           ` Fwd: " Pavel Machek
2008-02-04 21:54             ` Abel Bernabeu
2008-02-04 22:48               ` Jiri Kosina
2008-02-04 23:13                 ` Abel Bernabeu
2008-02-04 23:39                   ` Pavel Machek
2008-02-04 20:31       ` Pavel Machek
2008-02-05  1:57 ` Jiri Kosina
2008-02-05 11:06   ` [regression] " Pavel Machek
2008-02-05 12:50     ` Jiri Kosina
2008-02-05 12:54       ` Ingo Molnar
2008-02-05 13:05         ` Jakub Jelinek
2008-02-05 16:18           ` Pavel Machek
2008-02-05 16:37             ` Ingo Molnar
2008-02-05 16:12       ` Pavel Machek
2008-02-05 13:08   ` Hugh Dickins
2008-02-05 15:00     ` Arjan van de Ven
2008-02-05 15:46       ` Pavel Machek
2008-02-05 15:49         ` Jiri Kosina
2008-02-05 15:55           ` Pavel Machek
2008-02-05 15:49         ` Ingo Molnar
2008-02-05 15:59           ` Pavel Machek
2008-02-05 16:06             ` Ingo Molnar
2008-02-05 22:03               ` Pavel Machek
2008-02-05 16:58         ` Arjan van de Ven
2008-02-05 17:33           ` Pavel Machek
2008-02-05 22:35           ` Jiri Kosina
2008-02-06  3:24             ` Randy Dunlap
2008-02-05 16:02   ` Pavel Machek [this message]
2008-02-05 16:09     ` Ingo Molnar
2008-02-05 22:04       ` Pavel Machek
2008-02-05 18:05   ` Pavel Machek
2008-02-05 20:42     ` Jiri Kosina

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