Re: [PATCH v2] scsi: virtio-scsi: Fix address translation failure ofHighMem pages used by sg list

[Wang Sen]

2012/7/25 Ben Hutchings <ben@xxxxxxxxxxxxxxx>:
> 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@xxxxxxxxxxxxxxxxxx>
> [...]
>
> This is not the correct way to submit a change for stable.  See
> Documentation/stable_kernel_rules.txt.

OK, thanks.

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



-- 
------------------------------------------
Wang Sen
Addr: XUPT,Xi'an,Shaanxi,China
Email: kelvin.xupt@xxxxxxxxx
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