Re: [Qemu-devel] [PULL V2 24/26] net: ignore packet size greater than INT_MAX

[Jason Wang <jasowang@redhat.com>]

On 2018/11/15 上午12:23, Dima Stepanov wrote:
> On Wed, Nov 14, 2018 at 10:59:32AM +0800, Jason Wang wrote:
>> On 2018/11/13 下午11:41, Dima Stepanov wrote:
>>> Hi Jason,
>>>
>>> I know that this patch has been already merged to stable, but i have a
>>> question:
>>>
>>> On Fri, Oct 19, 2018 at 11:22:23AM +0800, Jason Wang wrote:
>>>> There should not be a reason for passing a packet size greater than
>>>> INT_MAX. It's usually a hint of bug somewhere, so ignore packet size
>>>> greater than INT_MAX in qemu_deliver_packet_iov()
>>>>
>>>> CC:qemu-stable@nongnu.org
>>>> Reported-by: Daniel Shapira<daniel@twistlock.com>
>>>> Reviewed-by: Michael S. Tsirkin<mst@redhat.com>
>>>> Signed-off-by: Jason Wang<jasowang@redhat.com>
>>>> ---
>>>>   net/net.c | 7 ++++++-
>>>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/net/net.c b/net/net.c
>>>> index c66847e..07c194a 100644
>>>> --- a/net/net.c
>>>> +++ b/net/net.c
>>>> @@ -712,10 +712,15 @@ ssize_t qemu_deliver_packet_iov(NetClientState *sender,
>>>>                                   void *opaque)
>>>>   {
>>>>       NetClientState *nc = opaque;
>>>> +    size_t size = iov_size(iov, iovcnt);
>>>>       int ret;
>>>> +    if (size > INT_MAX) {
>>>> +        return size;
>>> Is it okay that the function returns ssize_t (signed), but the type of the
>>> size variable is size_t (unsigned)? For now the top level routine checks
>>> the return value only for 0, but anyway we can return negative value
>>> here instead of positive. What do you think?
>>>
>>> Regards, Dima.
>>>
>> Any non zero value should be ok here. Actually I think because of the
>> conversion from size_t to ssize_t, caller actually see negative value?
> I believe it depends. If long (ssize_t and size_t type) is 8 bytes, then
> the routine can sometimes return positive values and sometimes negative.
> I fully agree that in the current case any non zero value should be
> okay. I just wanted to point on the inconsistency in types and as a
> result a return value.


I see, want to post a patch for this?

Thanks


> Dima.
>> Thanks
>>