linux-kernel - Re: KVM segfaults with 3.5 while installing ubuntu 12.04

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Date:	Mon, 06 Aug 2012 15:11:53 +0200
From:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
To:	Avi Kivity <avi@...hat.com>
CC:	mtosatti@...hat.com, kvm@...r.kernel.org,
	qemu-devel <qemu-devel@...gnu.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kevin Wolf <kwolf@...hat.com>,
	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>
Subject: Re: KVM segfaults with 3.5 while installing ubuntu 12.04

can confirm - this fixed it!
Am 06.08.2012 14:37, schrieb Avi Kivity:
> On 08/06/2012 03:12 PM, Avi Kivity wrote:
>> On 08/06/2012 11:46 AM, Stefan Priebe - Profihost AG wrote:
>>
>>> But still i got the segfault and core dump - this is my main problem? I
>>> mean qemu-kvm master isn't declared as stable. So i don't care about the
>>> slowness here.
>>>
>>> What can we do about the core dump and crash?
>>
>> Okay, I reproduced it; it seems aio=native is the culprit.  You can try
>> aio=threads as a workaround.
>>
>> Copying some relevant people (context: aio=native on qemu-kvm-1.1.1
>> segfaults pretty early during guest install)
>>
>
> The following ought to fix it:
>
>
> From: Avi Kivity <avi@...hat.com>
> Date: Mon, 6 Aug 2012 15:35:02 +0300
> Subject: [PATCH] virtio-mlk: fix use-after-free while handling scsi commands
>
> The scsi passthrough handler falls through after completing a
> request into the failure path, resulting in a use after free.
>
> Reprducible by running a guest with aio=native on a block device.
>
> Reported-by: Stefan Priebe <s.priebe@...fihost.ag>
> Signed-off-by: Avi Kivity <avi@...hat.com>
>
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index f21757e..552b3b6 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -254,6 +254,7 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>
>       virtio_blk_req_complete(req, status);
>       g_free(req);
> +    return;
>   #else
>       abort();
>   #endif
>
>
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