linux-kernel - Re: [RFC PATCH] virtio_blk: Checking "private_data" to avoid kernel panic when hotplugging

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Message-ID: <4F84F7BC.102@cn.fujitsu.com>
Date:	Wed, 11 Apr 2012 11:17:16 +0800
From:	Ren Mingxin <renmx@...fujitsu.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	Kay Sievers <kay.sievers@...y.org>,
	Tokunaga Kei <tokunaga.keiich@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	UDEV <linux-hotplug@...r.kernel.org>
Subject: Re: [RFC PATCH] virtio_blk: Checking "private_data"  to avoid kernel
 panic when hotplugging

  On 04/09/2012 03:53 PM, Michael S. Tsirkin wrote:
> On Wed, Mar 28, 2012 at 11:40:33AM +0800, Ren Mingxin wrote:
>> On guest with upstream's kernel(3.3.0-rc7), I
>> mounted virtblk as:
>>    a) # mkfs /dev/vda
>>    b) # mount /dev/vda /mnt
>>    c) # cd /mnt
>>
>> Then I did hotplug for virtblk via virsh on host as:
>>    a) # sudo virsh detach-disk guest vda
>>    b) # sudo virsh attach-disk guest /media/data/test.img vda
>>
>> I encountered guest's kernel panic (*probability*
>> *event*)whose backtrace liked this:
> Any news here? Managed to trace?

Sorry, I had a leave last week.

> Does this still happen with 3.4-rc2?

I retested this with 3.4-rc2, but the panic couldn't be reproduced.
(Last time, It seemed that the upstream's kernel was 3.3-rc7)

> There's a chance you are hitting a race fixed by
> 4678d6f970c2f7c0cbfefc0cc666432d153b321b.
>
> If it's still not fixed it might make sense to enable slab debugging -
> we might have a use after free here.
>

I don't think the below commit has fixed this panic issue, for it is 
included
in my last test environment(3.3-rc7).
4678d6f970c2f7c0cbfefc0cc666432d153b321b

Now, I'd find which commit makes sense.

-- 
Thanks,
Ren

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