4.20-stable review patch. If anyone has any objections, please let me know.
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From: Xin Long lucien.xin@gmail.com
[ Upstream commit ecf938fe7d0088077ee1280419a2b3c5429b47c8 ]
Now sctp_transport_pmtu() passes transport->saddr into .get_dst() to set flow sport from 'saddr'. However, transport->saddr is set only when transport->dst exists in sctp_transport_route().
If sctp_transport_pmtu() is called without transport->saddr set, like when transport->dst doesn't exists, the flow sport will be set to 0 from transport->saddr, which will cause a wrong route to be got.
Commit 6e91b578bf3f ("sctp: re-use sctp_transport_pmtu in sctp_transport_route") made the issue be triggered more easily since sctp_transport_pmtu() would be called in sctp_transport_route() after that.
In gerneral, fl4->fl4_sport should always be set to htons(asoc->base.bind_addr.port), unless transport->asoc doesn't exist in sctp_v4/6_get_dst(), which is the case:
sctp_ootb_pkt_new() -> sctp_transport_route()
For that, we can simply handle it by setting flow sport from saddr only when it's 0 in sctp_v4/6_get_dst().
Fixes: 6e91b578bf3f ("sctp: re-use sctp_transport_pmtu in sctp_transport_route") Reported-by: Ying Xu yinxu@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/ipv6.c | 3 ++- net/sctp/protocol.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-)
--- a/net/sctp/ipv6.c +++ b/net/sctp/ipv6.c @@ -277,7 +277,8 @@ static void sctp_v6_get_dst(struct sctp_
if (saddr) { fl6->saddr = saddr->v6.sin6_addr; - fl6->fl6_sport = saddr->v6.sin6_port; + if (!fl6->fl6_sport) + fl6->fl6_sport = saddr->v6.sin6_port;
pr_debug("src=%pI6 - ", &fl6->saddr); } --- a/net/sctp/protocol.c +++ b/net/sctp/protocol.c @@ -440,7 +440,8 @@ static void sctp_v4_get_dst(struct sctp_ } if (saddr) { fl4->saddr = saddr->v4.sin_addr.s_addr; - fl4->fl4_sport = saddr->v4.sin_port; + if (!fl4->fl4_sport) + fl4->fl4_sport = saddr->v4.sin_port; }
pr_debug("%s: dst:%pI4, src:%pI4 - ", __func__, &fl4->daddr,