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    Subject[PATCH 4.18 023/135] sctp: update dst pmtu with the correct daddr
    Date
    4.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Xin Long <lucien.xin@gmail.com>

    [ Upstream commit d7ab5cdce54da631f0c8c11e506c974536a3581e ]

    When processing pmtu update from an icmp packet, it calls .update_pmtu
    with sk instead of skb in sctp_transport_update_pmtu.

    However for sctp, the daddr in the transport might be different from
    inet_sock->inet_daddr or sk->sk_v6_daddr, which is used to update or
    create the route cache. The incorrect daddr will cause a different
    route cache created for the path.

    So before calling .update_pmtu, inet_sock->inet_daddr/sk->sk_v6_daddr
    should be updated with the daddr in the transport, and update it back
    after it's done.

    The issue has existed since route exceptions introduction.

    Fixes: 4895c771c7f0 ("ipv4: Add FIB nexthop exceptions.")
    Reported-by: ian.periam@dialogic.com
    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sctp/transport.c | 12 ++++++++++--
    1 file changed, 10 insertions(+), 2 deletions(-)

    --- a/net/sctp/transport.c
    +++ b/net/sctp/transport.c
    @@ -260,6 +260,7 @@ void sctp_transport_pmtu(struct sctp_tra
    bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
    {
    struct dst_entry *dst = sctp_transport_dst_check(t);
    + struct sock *sk = t->asoc->base.sk;
    bool change = true;

    if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
    @@ -271,12 +272,19 @@ bool sctp_transport_update_pmtu(struct s
    pmtu = SCTP_TRUNC4(pmtu);

    if (dst) {
    - dst->ops->update_pmtu(dst, t->asoc->base.sk, NULL, pmtu);
    + struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family);
    + union sctp_addr addr;
    +
    + pf->af->from_sk(&addr, sk);
    + pf->to_sk_daddr(&t->ipaddr, sk);
    + dst->ops->update_pmtu(dst, sk, NULL, pmtu);
    + pf->to_sk_daddr(&addr, sk);
    +
    dst = sctp_transport_dst_check(t);
    }

    if (!dst) {
    - t->af_specific->get_dst(t, &t->saddr, &t->fl, t->asoc->base.sk);
    + t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
    dst = t->dst;
    }


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