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

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Message-ID: <20120409075318.GB27771@redhat.com>
Date:	Mon, 9 Apr 2012 10:53:18 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Ren Mingxin <renmx@...fujitsu.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 Wed, Mar 28, 2012 at 11:40:33AM +0800, Ren Mingxin wrote:
>  Hi,
> 
> 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?
Does this still happen with 3.4-rc2?
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.

-- 
MST
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