On Sun, 2017-04-02 at 13:45 +0200, Florian Westphal wrote:
> Eric Dumazet <eric.duma...@gmail.com> wrote:
> > - for (i = sizeof(struct tcphdr); i <= tcp_hdrlen - TCPOLEN_MSS; i +=
> > optlen(opt, i)) {
> > + for (i = sizeof(struct tcphdr); i < tcp_hdrlen - TCPOLEN_MSS; i +=
> > optlen(opt, i)) {
> > if (opt[i] == TCPOPT_MSS && opt[i+1] == TCPOLEN_MSS) {
> > u_int16_t oldmss;
>
> maybe I am low on caffeeine but this looks fine, for tcp header with
> only tcpmss this boils down to "20 <= 24 - 4" so we acccess offsets 20-23
> which seems ok.
I am definitely low on caffeine ;)
An issue in this function is that we might add the missing MSS option,
without checking that TCP options are already full.
But this should not cause a KASAN splat, only some malformed TCP packet
(tcph->doff would wrap)
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