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.xin@xxxxxxxxx>
> > Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> > ---
> > 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.
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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