linux-kernel - Re: [PATCH 1/2] utrace core

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Date:	Thu, 28 Aug 2008 02:00:50 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] utrace core

On Thu, Aug 28, 2008 at 01:46:52AM +0400, Alexey Dobriyan wrote:
> On Thu, Aug 28, 2008 at 01:32:11AM +0400, Alexey Dobriyan wrote:
> > > And run to confirm that attach/detach/exec program still crashes it.
> > > There is PREEMPT_RCU now so it will be even more not funny.
> > 
> > As promised, quickly reproducible via expt_ptratt.c:
> 
> Another one:

And overwritten poison if run in parallel with

	while true; do
		killall -9 expl_ptratt
		killall -9 exe
	done

=============================================================================
BUG utrace: Poison overwritten
-----------------------------------------------------------------------------

INFO: 0xffff88017c31e7b0-0xffff88017c31e7f0. First byte 0x6c instead of 0x6b
INFO: Allocated in utrace_attach_task+0x1f4/0x3d0 age=13 cpu=1 pid=5377
INFO: Freed in utrace_free+0x16/0x20 age=5 cpu=1 pid=5377
INFO: Slab 0xffffe2000532ae90 objects=21 used=2 fp=0xffff88017c31e780 flags=0x80000000000000c3
INFO: Object 0xffff88017c31e780 @offset=1920 fp=0xffff88017c31e540

Bytes b4 0xffff88017c31e770:  fc 1f ff ff 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ü.ÿÿ....ZZZZZZZZ
  Object 0xffff88017c31e780:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
  Object 0xffff88017c31e790:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
  Object 0xffff88017c31e7a0:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
  Object 0xffff88017c31e7b0:  6c 6c 6b 6b 6b 6b 6b 6b ff ff ff ff 6b 6b 6b 6b llkkkkkkÿÿÿÿkkkk
  Object 0xffff88017c31e7c0:  ff ff ff ff ff ff ff ff 6b 6b 6b 6b 6b 6b 6b 6b ÿÿÿÿÿÿÿÿkkkkkkkk
  Object 0xffff88017c31e7d0:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
  Object 0xffff88017c31e7e0:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
  Object 0xffff88017c31e7f0:  6a 6b 6b 6b 6b 6b 6b a5                         jkkkkkk¥        
 Redzone 0xffff88017c31e7f8:  bb bb bb bb bb bb bb bb                         »»»»»»»»        
 Padding 0xffff88017c31e838:  5a 5a 5a 5a 5a 5a 5a 5a                         ZZZZZZZZ        
Pid: 5382, comm: expl_ptratt Tainted: G        W 2.6.27-rc4-next-20080827-utrace #5
Call Trace:
 [<ffffffff8028f989>] print_trailer+0xf9/0x160
 [<ffffffff8028ff75>] check_bytes_and_report+0xa5/0xd0
 [<ffffffff80290048>] check_object+0xa8/0x250
 [<ffffffff80291173>] __slab_alloc+0x4f3/0x670
 [<ffffffff8025f304>] ? utrace_attach_task+0x1f4/0x3d0
 [<ffffffff8025f304>] ? utrace_attach_task+0x1f4/0x3d0
 [<ffffffff80291721>] kmem_cache_alloc+0xb1/0xd0
 [<ffffffff8025f304>] utrace_attach_task+0x1f4/0x3d0
 [<ffffffff8023b977>] ptrace_attach_utrace+0x27/0x80
 [<ffffffff8023c3e8>] ptrace_attach+0x48/0x1b0
 [<ffffffff8023c610>] sys_ptrace+0xc0/0xd0
 [<ffffffff8020b73b>] system_call_fastpath+0x16/0x1b
FIX utrace: Restoring 0xffff88017c31e7b0-0xffff88017c31e7f0=0x6b

FIX utrace: Marking all objects used

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