linux-kernel - Re: 3.4-rc7: BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1 val:-59

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Date:	Wed, 30 May 2012 16:22:31 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Martin Mokrejs <mmokrejs@...d.natur.cuni.cz>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"markus@...ppelsdorf.de" <markus@...ppelsdorf.de>,
	"hughd@...gle.com" <hughd@...gle.com>,
	"kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: 3.4-rc7: BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1
 val:-59

Martin Mokrejs wrote:
>
>
> Konstantin Khlebnikov wrote:
>> Martin Mokrejs wrote:
>>> Andrew Morton wrote:
>>>> On Wed, 30 May 2012 00:18:31 +0400
>>>> Konstantin Khlebnikov<khlebnikov@...nvz.org>   wrote:
>>>>
>>>>> Oleg Nesterov wrote:
>>>>>> On 05/22, Andrew Morton wrote:
>>>>>>>
>>>>>>> Also, I have a note here that Oleg was unhappy with the patch.  Oleg
>>>>>>> happiness is important.  Has he cheered up yet?
>>>>>>
>>>>>> Well, yes, I do not really like this patch ;) Because I think there is
>>>>>> a more simple/straightforward fix, see below. In my opinion it also
>>>>>> makes the original code simpler.
>>>>>>
>>>>>> But. Obviously this is subjective, I can't prove my patch is "better",
>>>>>> and I didn't try to test it.
>>>>>>
>>>>>> So I won't argue with Konstantin who dislikes my patch, although I
>>>>>> would like to know the reason.
>>>>>
>>>>> I don't remember why I dislike your patch.
>>>>> For now I can only say ACK )
>>>>
>>>> We'll need a changelogged signed-off patch, please Oleg.  And some evidence
>>>> that it was tested would be nice ;)
>>>
>>> I will reboot in few hours, finally after few days ... I am running this first
>>> patch. I will try to test the second/alternative patch more quickly. Sorry for
>>> the delay.
>>>
>>
>> easiest way trigger this bug:
>>
>> #define _GNU_SOURCE
>> #include<unistd.h>
>> #include<sched.h>
>> #include<sys/syscall.h>
>> #include<sys/mman.h>
>>
>> static inline int sys_clone(unsigned long flags, void *stack, int *ptid, int *ctid)
>> {
>>      return syscall(SYS_clone, flags, stack, ptid, ctid);
>> }
>>
>> int main(int argc, char **argv)
>> {
>>      void *page;
>>
>>      page = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
>>      sys_clone(CLONE_VFORK | CLONE_VM | CLONE_CHILD_CLEARTID, NULL, NULL, page);
>> }
>>
>
> I am getting segfaults with this.
>
> (gdb) where
> #0  0x0000000000000000 in ?? ()
> #1  0x00007f430f70a7e0 in __elf_set___libc_subfreeres_element_free_mem__ () from /lib64/libc.so.6
> #2  0x00007f430f70a7e8 in __elf_set___libc_atexit_element__IO_cleanup__ () from /lib64/libc.so.6
> #3  0x0000000000000001 in ?? ()
> #4  0x0000000000000000 in ?? ()
> (gdb)
>
> What number should I give it as an argument? ;-)

there is no arguments.

yeah it corrupts stack. I'm too lazy to write it properly =)
but on non-patched kernel it also triggers this bug:
[206732.025131] BUG: Bad rss-counter state mm:ffff88000d8a6c80 idx:1 val:-1

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