Re: [Qemu-devel] [PATCH v2] virtio: add check for descriptor's mapped address

[Laurent Vivier]

On 19/09/2016 18:59, Laszlo Ersek wrote:
> On 09/19/16 17:55, Stefan Hajnoczi wrote:
>> On Mon, Sep 19, 2016 at 02:36:11PM +0530, P J P wrote:
>>> From: Prasad J Pandit <address@hidden>
>>>
>>> virtio back end uses set of buffers to facilitate I/O operations.
>>> If its size is too large, 'cpu_physical_memory_map' could return
>>> a null address. This would result in a null dereference while
>>> un-mapping descriptors. Add check to avoid it.
>>>
>>> Reported-by: Qinghao Tang <address@hidden>
>>> Signed-off-by: Prasad J Pandit <address@hidden>
>>> ---
>>>  hw/virtio/virtio.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> Update per:
>>>   -> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg03889.html
>>>
>>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>>> index 15ee3a7..311dd0b 100644
>>> --- a/hw/virtio/virtio.c
>>> +++ b/hw/virtio/virtio.c
>>> @@ -472,6 +472,11 @@ static void virtqueue_map_desc(unsigned int *p_num_sg, 
>>> hwaddr *addr, struct iove
>>>          }
>>>  
>>>          iov[num_sg].iov_base = cpu_physical_memory_map(pa, &len, is_write);
>>> +        if (!iov[num_sg].iov_base) {
>>> +            error_report("virtio: bogus descriptor or out of resources");
>>> +            exit(EXIT_FAILURE);
>>
>> exit(1) is used everywhere else in the file (including just a few lines
>> above in the same function).  Please use exit(1) for consistency.
> 
> Laurent's pending series
> 
> [Qemu-devel] [PATCH 00/26] trivial: use exit(EXIT_SUCCESS) and
>                            exit(EXIT_FAILURE)
> 
> specifically his patch
> 
> [Qemu-devel] [PATCH 11/26] pci, virtio: use exit(EXIT_SUCCESS) and
>                            exit(EXIT_FAILURE)
> 
> converts the argument of the exit() that you name to EXIT_FAILURE.
> 
> So using EXIT_FAILURE in Prasad's patch is actually what will uphold
> consistency.
> 
>> Looks fine otherwise.
>>

Laszlo, it seems Peter (and some others) would prefer to use exit(1)
instead of exit(EXIT_FAILURE), so I don't think my series will be applied.

Laurent