LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Pavel Machek <pavel@ucw.cz>
To: Ingo Molnar <mingo@elte.hu>
Cc: jikos@suse.cz, kernel list <linux-kernel@vger.kernel.org>
Subject: Re: brk randomization breaks columns
Date: Mon, 4 Feb 2008 14:28:53 +0100	[thread overview]
Message-ID: <20080204132853.GA4630@elf.ucw.cz> (raw)
In-Reply-To: <20080204130156.GA8730@elte.hu>

Hi!

> > Hmm, code in binfmt_elf is really strange.
> > 
> >         elf_bss += load_bias;
> >         elf_brk += load_bias;
> >         start_code += load_bias;
> >         end_code += load_bias;
> >         start_data += load_bias;
> >         end_data += load_bias;
> > 
> >         /* Calling set_brk effectively mmaps the pages that we need
> >          * for the bss and break sections.  We must do this before
> >          * mapping in the interpreter, to make sure it doesn't wind
> >          * up getting placed where the bss needs to go.
> >          */
> >         retval = set_brk(elf_bss, elf_brk);
> > 
> > ... so we allocate non-randoimzed brk, but later we just overwrite bss 
> > variable with new, shiner and better randomized value... without 
> > unmapping the old one... The code in binfmt_elf.c is really a mess.
> 
> 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?]

Not sure this helps... If I only randomize _end_ of heap, it still
works. If I try to randomize beggining of heap, too, it will not even
start recent binaries :-(.
								Pavel

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 18ed6dd..9afc58f 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -980,6 +983,16 @@ #endif
 	}
 
 	loc->elf_ex.e_entry += load_bias;
+
+
+	printk("%d: %x\n", current->pid, elf_brk);
+
+	extern unsigned long 	randomize_range(unsigned long start, unsigned long end, unsigned long len);
+
+	long random = randomize_range(0, 0x200000, 0);
+	elf_brk += random;
+//	elf_bss += random;
+
 	elf_bss += load_bias;
 	elf_brk += load_bias;
 	start_code += load_bias;
@@ -1076,12 +1093,6 @@ #endif /* ARCH_HAS_SETUP_ADDITIONAL_PAGE
 	current->mm->end_data = end_data;
 	current->mm->start_stack = bprm->p;
 
-#ifdef arch_randomize_brk
-	if (current->flags & PF_RANDOMIZE)
-		current->mm->brk = current->mm->start_brk =
-			arch_randomize_brk(current->mm);
-#endif
-
 	if (current->personality & MMAP_PAGE_ZERO) {
 		/* Why this, you ask???  Well SVr4 maps page 0 as read-only,
 		   and some applications "depend" upon this behavior.

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

  reply	other threads:[~2008-02-04 13:28 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080204132853.GA4630@elf.ucw.cz \
    --to=pavel@ucw.cz \
    --cc=jikos@suse.cz \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --subject='Re: brk randomization breaks columns' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).