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

[Laszlo Ersek]

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.
> 

Thanks!
Laszlo