linux-kernel - Re: brk randomization breaks columns

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Message-ID: <20080205155959.GC24331@elf.ucw.cz>
Date:	Tue, 5 Feb 2008 16:59:59 +0100
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Hugh Dickins <hugh@...itas.com>, Jiri Kosina <jkosina@...e.cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	Abel Bernabeu <abel.bernabeu@...il.com>
Subject: Re: brk randomization breaks columns

On Tue 2008-02-05 16:49:53, Ingo Molnar wrote:
> 
> * Pavel Machek <pavel@....cz> wrote:
> 
> > Hi!
> > 
> > > > In my usual dither, I'm rather hoping Arjan will have a clear answer.
> > > 
> > > 
> > > setarch works. If the apps come in source form they need fixing anyway (since I'd not be
> > > surprised of current gcc reorders variables), if not.. we only have 2 cases,
> > > the other case was the build process of emacs (which got fixed 5
> > > years ago).
> > 
> > uemacs ... broken with randomization
> > colums, sss ... local programs, broken with randomization
> > procinfo ... broken, randomization makes it die sooner.
> > mikmod ... broken with randomization
> > bsdsed ... broken with randomization
> > ...
> > Should I test few more?
> 
> just a quick debug question: do they all work if you start them via 
> setarch?

I was actually toggling randomization with 

echo 0|1 > /proc/sys/kernel/randomize_va_space

. Yes, setarch i386 -R /usr/local/bin/uemacs (etc) fixes them, too.
	
What about this?

Heap randomization breaks /lib/libc.so.5.4.33, make it possible to
randomize normal stuff but leave the heap alone.

Signed-off-by: Pavel Machek <pavel@...e.cz>


diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 18ed6dd..4b099ea 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1077,7 +1077,7 @@ #endif /* ARCH_HAS_SETUP_ADDITIONAL_PAGE
 	current->mm->start_stack = bprm->p;
 
 #ifdef arch_randomize_brk
-	if (current->flags & PF_RANDOMIZE)
+	if ((current->flags & PF_RANDOMIZE) && (randomize_va_space > 1))
 		current->mm->brk = current->mm->start_brk =
 			arch_randomize_brk(current->mm);
 #endif

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