On Thu, May 19, 2016 at 3:50 PM, Hannes Frederic Sowa
<han...@stressinduktion.org> wrote:
> Hi Cong,
>
> On Fri, May 20, 2016, at 00:33, Cong Wang wrote:
>> On Thu, May 19, 2016 at 6:58 AM, Hannes Frederic Sowa
>> <han...@stressinduktion.org> wrote:
>> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
>> > index 2e3ebfe5549ef5..d56c0559b477cb 100644
>> > --- a/net/ipv4/udp.c
>> > +++ b/net/ipv4/udp.c
>> > @@ -1565,7 +1565,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct
>> > sk_buff *skb)
>> >
>> > /* if we're overly short, let UDP handle it */
>> > encap_rcv = ACCESS_ONCE(up->encap_rcv);
>> > - if (skb->len > sizeof(struct udphdr) && encap_rcv) {
>> > + if (encap_rcv) {
>>
>>
>> I don't think you can just remove it here, l2tp_udp_recv_core() still
>> relies on it:
>>
>> /* UDP has verifed checksum */
>>
>> /* UDP always verifies the packet length. */
>> __skb_pull(skb, sizeof(struct udphdr));
>
> I think this is fine, we check on every entrance to udp that we may pull
> (pskb_may_pull) an udphdr but we really never pull the header. At this
> point we are guaranteed to have skb->len of at least sizeof(struct
> udphdr).
Ah, yeah, __udp4_lib_rcv().
BTW, this part (the second half) of your patch is an optimization,
the rest (the first half) is a real bug fix. It makes sense to split
them if you plan to backport it to -stable.
Thanks.
