The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 02dc2ee7c7476dd831df63d2b10cc0a162a531f1 Mon Sep 17 00:00:00 2001

From: Xin Long lucien.xin@gmail.com Date: Wed, 21 Jul 2021 14:45:54 -0400 Subject: [PATCH] sctp: do not update transport pathmtu if SPP_PMTUD_ENABLE is not set

Currently, in sctp_packet_config(), sctp_transport_pmtu_check() is called to update transport pathmtu with dst's mtu when dst's mtu has been changed by non sctp stack like xfrm.

However, this should only happen when SPP_PMTUD_ENABLE is set, no matter where dst's mtu changed. This patch is to fix by checking SPP_PMTUD_ENABLE flag before calling sctp_transport_pmtu_check().

Thanks Jacek for reporting and looking into this issue.

v1->v2: - add the missing "{" to fix the build error.

Fixes: 69fec325a643 ('Revert "sctp: remove sctp_transport_pmtu_check"') Reported-by: Jacek Szafraniec jacek.szafraniec@nokia.com Tested-by: Jacek Szafraniec jacek.szafraniec@nokia.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

diff --git a/net/sctp/output.c b/net/sctp/output.c index 9032ce60d50e..4dfb5ea82b05 100644 --- a/net/sctp/output.c +++ b/net/sctp/output.c @@ -104,8 +104,8 @@ void sctp_packet_config(struct sctp_packet *packet, __u32 vtag, if (asoc->param_flags & SPP_PMTUD_ENABLE) sctp_assoc_sync_pmtu(asoc); } else if (!sctp_transport_pl_enabled(tp) && - !sctp_transport_pmtu_check(tp)) { - if (asoc->param_flags & SPP_PMTUD_ENABLE) + asoc->param_flags & SPP_PMTUD_ENABLE) { + if (!sctp_transport_pmtu_check(tp)) sctp_assoc_sync_pmtu(asoc); }