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

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Date:	Mon, 06 Aug 2012 15:37:54 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
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

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


-- 
error compiling committee.c: too many arguments to function
--
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