Re: KVM segfaults with 3.5 while installing ubuntu 12.04

From: Stefan Priebe - Profihost AG
Date: Mon Aug 06 2012 - 09:11:53 EST


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@xxxxxxxxxx>
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@xxxxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>

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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