Re: [origin tree SLAB corruption] BUG kmalloc-64: Poisonoverwritten, INFO: Allocated in bdi_alloc_work+0x2b/0x100 age=175cpu=1 pid=3514
From: Jens Axboe
Date: Mon Sep 14 2009 - 05:20:51 EST
On Mon, Sep 14 2009, Pekka Enberg wrote:
>
* Eric Paris <eparis@xxxxxxxxxx> wrote:
>
>> On Sat, 2009年09月12日 at 09:24 +0200, Ingo Molnar wrote:
>
>> > James - i did not see a security pull request email from you in my
>
>> > lkml folder so i created this new thread. -tip testing found the
>
>> > easy crash below. It reverts cleanly so i went that easy route.
>
>> >
>
>> > At a really quick 10-seconds glance the crash happens because we
>
>> > destroy the slab cache twice, if the sysctl is toggled twice?
>
>>
>
>> Something a lot worse than SELinux here. I added this exact code and
>
>> got this warning. Something is wrong in the world of
>
>> kmem_cache_destroy.....
>
>
Btw, the kmem_cache_destroy() bug Eric found is not in Linu's tree yet.
>
>
On Mon, Sep 14, 2009 at 10:16 AM, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> -tip testing just triggered another type of SLAB problem (this time
>
> not apparently related to the security subsystem):
>
>
>
> BUG kmalloc-64: Poison overwritten
>
> -----------------------------------------------------------------------------
>
>
>
> INFO: 0xf498f6a0-0xf498f6a7. First byte 0x90 instead of 0x6b
>
> INFO: Allocated in bdi_alloc_work+0x2b/0x100 age=175 cpu=1 pid=3514
>
> INFO: Freed in bdi_work_free+0x45/0x60 age=9 cpu=1 pid=3509
>
> INFO: Slab 0xc3257d84 objects=36 used=11 fp=0xf498f690 flags=0x400000c3
>
> INFO: Object 0xf498f690 @offset=1680 fp=0xf498fe00
>
>
>
> Bytes b4 0xf498f680: ab 0d 00 00 9c 27 ff ff 5a 5a 5a 5a 5a 5a 5a 5a «....'ÿÿZZZZZZZZ
>
> Object 0xf498f690: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>
> Object 0xf498f6a0: 90 f3 98 f4 60 3c 11 c1 6b 6b 6b 6b 6b 6b 6b 6b .ó.ô`<.Ákkkkkkkk
>
>
This would be use-after-free in kmalloc-64 cache. Given the trace and
>
the fact that bdi_work_alloc() got introduce recently, it seems more
>
likely that fs/fs-writeback.c is to blame here. Jens, does the warning
>
ring a bell to you?
No bells, the code seems right to me. I'll prod at it a bit more. I
haven't seen anything like this during testing.
--
Jens Axboe
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
http://vger.kernel.org/majordomo-info.html
Please read the FAQ at
http://www.tux.org/lkml/