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From: Pavel Machek <pavel@ucw.cz>
To: Jiri Kosina <jkosina@suse.cz>
Cc: Ingo Molnar <mingo@elte.hu>, kernel list <linux-kernel@vger.kernel.org>
Subject: Re: brk randomization breaks columns
Date: Mon, 4 Feb 2008 21:31:09 +0100	[thread overview]
Message-ID: <20080204203109.GA1545@elf.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.64.0802041635000.30955@jikos.suse.cz>

On Mon 2008-02-04 17:12:43, Jiri Kosina wrote:
> On Mon, 4 Feb 2008, Jiri Kosina wrote:
> 
> > 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.
> 
> And I really think that (at least Pavel's version of) libc.so.5 is making 
> some strange assumptions about memory layout of the process, which could 
> also explain the other failures.
> 
> Pavel, could you please link the source code below against libc.so.5 with 
> brk randomization turned on, and show the output, and if it segfaults, 
> send the backtrace at the time of the crash? I suspect that it will crash 
> somewhere in exit path when calling .dtor functions, as it will try to 
> perform some cleanup in unmapped area. Thanks.
> 
> #include <unistd.h>
> #include <stdio.h>
> #include <stdlib.h>
> 
> int main()
> {
>         int *curr_brk = sbrk(0);
>         char command[1024];
> 
>         sprintf(command, "/bin/cat /proc/%d/maps", getpid());
> 
>         printf("brk set to %p\n", curr_brk);
>         system(command);
> 
>         brk(curr_brk + 0x00001000);
>         curr_brk = sbrk(0);
> 
>         printf("brk set to %p\n", curr_brk);
>         system(command);
>         exit(0);
> }

This one seems to work, even with randomization:

guest@amd:~$ gcc test2.c -nostdlib /lib/libc.so.5.4.33 -o test2
/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to
0000000008048340
guest@amd:~$ ./test2
brk set to 0x8b1b000
08048000-08049000 r-xp 00000000 08:04 423985     /home/guest/test2
08049000-0804a000 rwxp 00000000 08:04 423985     /home/guest/test2
b7eb7000-b7eb8000 rwxp b7eb7000 00:00 0
b7eb8000-b7f3f000 r-xp 00000000 08:04 373330     /lib/libc.so.5.4.33
b7f3f000-b7f45000 rwxp 00086000 08:04 373330     /lib/libc.so.5.4.33
b7f45000-b7f78000 rwxp b7f45000 00:00 0
b7f92000-b7f95000 rwxp b7f92000 00:00 0
b7f95000-b7fb1000 r-xp 00000000 08:04 194956     /lib/ld-2.7.so
b7fb1000-b7fb3000 rwxp 0001b000 08:04 194956     /lib/ld-2.7.so
bf89e000-bf8b2000 rwxp bffeb000 00:00 0          [stack]
bf8b2000-bf8b3000 rw-p bffff000 00:00 0
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
brk set to 0x8b1f000
08048000-08049000 r-xp 00000000 08:04 423985     /home/guest/test2
08049000-0804a000 rwxp 00000000 08:04 423985     /home/guest/test2
08b1b000-08b1f000 rwxp 08b1b000 00:00 0          [heap]
b7eb7000-b7eb8000 rwxp b7eb7000 00:00 0
b7eb8000-b7f3f000 r-xp 00000000 08:04 373330     /lib/libc.so.5.4.33
b7f3f000-b7f45000 rwxp 00086000 08:04 373330     /lib/libc.so.5.4.33
b7f45000-b7f78000 rwxp b7f45000 00:00 0
b7f92000-b7f95000 rwxp b7f92000 00:00 0
b7f95000-b7fb1000 r-xp 00000000 08:04 194956     /lib/ld-2.7.so
b7fb1000-b7fb3000 rwxp 0001b000 08:04 194956     /lib/ld-2.7.so
bf89e000-bf8b2000 rwxp bffeb000 00:00 0          [stack]
bf8b2000-bf8b3000 rw-p bffff000 00:00 0
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
guest@amd:~$

But if I compile it on my system, test2 uses ld-linux.so.2, not
ld-linux.so.1. columns use ld-linux.so.1, but I can't compile binary
like that with my toolchain.

									Pavel

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

  parent reply	other threads:[~2008-02-04 20:31 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 [this message]
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

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