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

[Jason Wang]

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:address@hidden
> > > > Reported-by: Daniel Shapira<address@hidden>
> > > > Reviewed-by: Michael S. Tsirkin<address@hidden>
> > > > Signed-off-by: Jason Wang<address@hidden>
> > > > ---
> > > >   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