On Fri, Apr 27, 2018 at 03:13:49PM -0300, Marcelo Ricardo Leitner wrote:
> On Fri, Apr 27, 2018 at 06:50:50AM -0400, Neil Horman wrote:
> > On Thu, Apr 26, 2018 at 04:58:52PM -0300, Marcelo Ricardo Leitner wrote:
> > > As noticed by Xin Long, the if() here is always true as PMTU can never
> > > be 0.
> > >
> > > Reported-by: Xin Long <lucien....@gmail.com>
> > > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
> > > ---
> > > net/sctp/associola.c | 6 ++----
> > > 1 file changed, 2 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> > > index
> > > b3aa95222bd52113295cb246c503c903bdd5c353..c5ed09cfa8423b17546e3d45f6d06db03af66384
> > > 100644
> > > --- a/net/sctp/associola.c
> > > +++ b/net/sctp/associola.c
> > > @@ -1397,10 +1397,8 @@ void sctp_assoc_sync_pmtu(struct sctp_association
> > > *asoc)
> > > pmtu = t->pathmtu;
> > > }
> > >
> > > - if (pmtu) {
> > > - asoc->pathmtu = pmtu;
> > > - asoc->frag_point = sctp_frag_point(asoc, pmtu);
> > > - }
> > > + asoc->pathmtu = pmtu;
> > > + asoc->frag_point = sctp_frag_point(asoc, pmtu);
> > >
> > Can you double check this? Looking at it, it seems far fetched, but if
> > someone
>
> Sure.
>
> > sends a crafted icmp dest unreach message to the host, pmtu_sending might be
> > able to get set for an association (which may have no transports established
> > yet), and if so, on the first packet send sctp_assoc_sync_pmtu can be
> > called,
> > leading to a fall through in the loop over all transports, and pmtu being
> > zero.
> > It seems like a far fetched set of circumstances, I know, but if it can
> > happen,
> > I think you might see a crash in sctp_frag_point due to an underflow of the
> > frag
> > value
>
> If I got you right, this situation would not happen because when
> handling the icmp it will check if there is a transport and ignore it
> otherwise.
>
Yup, you're right. sctp_err_lookup returns NULL if there is no transport
associated with the icmp message
Thanks
Neil
> Marcelo
>
> >
> > Neil
> >
> > > pr_debug("%s: asoc:%p, pmtu:%d, frag_point:%d\n", __func__, asoc,
> > > asoc->pathmtu, asoc->frag_point);
> > > --
> > > 2.14.3
> > >
> > >
> > --
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> >
>
