linux-kernel - Re: [PATCH v2] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list

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Message-ID: <1343218896.5132.135.camel@deadeye.wl.decadent.org.uk>
Date:	Wed, 25 Jul 2012 13:21:36 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Wang Sen <senwang@...ux.vnet.ibm.com>
Cc:	linux-scsi@...r.kernel.org, JBottomley@...allels.com,
	pbonzini@...hat.com, stefanha@...ux.vnet.ibm.com,
	mc@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] scsi: virtio-scsi: Fix address translation failure
 of HighMem pages used by sg list

On Wed, 2012-07-25 at 20:13 +0800, Wang Sen wrote:
> When using the commands below to write some data to a virtio-scsi LUN of the
> QEMU guest(32-bit) with 1G physical memory(qemu -m 1024), the qemu will crash.
> 
>         # sudo mkfs.ext4 /dev/sdb  (/dev/sdb is the virtio-scsi LUN.)
>         # sudo mount /dev/sdb /mnt
>         # dd if=/dev/zero of=/mnt/file bs=1M count=1024
> 
> In current implementation, sg_set_buf is called to add buffers to sg list which
> is put into the virtqueue eventually. But if there are some HighMem pages in
> table->sgl you can not get virtual address by sg_virt. So, sg_virt(sg_elem) may
> return NULL value. This will cause QEMU exit when virtqueue_map_sg is called
> in QEMU because an invalid GPA is passed by virtqueue.
> 
> I take Paolo's solution mentioned in last thread to avoid failure on handling 
> flag bits.
> 
> I have tested the patch on my workstation. QEMU would not crash any more.
>
> Signed-off-by: Wang Sen <senwang@...ux.vnet.ibm.com>
[...]

This is not the correct way to submit a change for stable.  See
Documentation/stable_kernel_rules.txt.

Ben.

-- 
Ben Hutchings
If more than one person is responsible for a bug, no one is at fault.

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