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From: Xin Long <>
To: network dev <>,
	Marcelo Ricardo Leitner <>
Subject: [PATCH] sctp: move sk_route_caps check and set into sctp_outq_flush_transports
Date: Fri, 19 Mar 2021 11:52:41 +0800	[thread overview]
Message-ID: <> (raw)

The sk's sk_route_caps is set in sctp_packet_config, and later it
only needs to change when traversing the transport_list in a loop,
as the dst might be changed in the tx path.

So move sk_route_caps check and set into sctp_outq_flush_transports
from sctp_packet_transmit. This also fixes a dst leak reported by
Chen Yi:

As calling sk_setup_caps() in sctp_packet_transmit may also set the
sk_route_caps for the ctrl sock in a netns. When the netns is being
deleted, the ctrl sock's releasing is later than dst dev's deleting,
which will cause this dev's deleting to hang and dmesg error occurs:

  unregister_netdevice: waiting for xxx to become free. Usage count = 1

Reported-by: Chen Yi <>
Fixes: bcd623d8e9fa ("sctp: call sk_setup_caps in sctp_packet_transmit instead")
Signed-off-by: Xin Long <>
 net/sctp/output.c   | 7 -------
 net/sctp/outqueue.c | 7 +++++++
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/sctp/output.c b/net/sctp/output.c
index 6614c9f..a6aa17d 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -584,13 +584,6 @@ int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 		goto out;
-	rcu_read_lock();
-	if (__sk_dst_get(sk) != tp->dst) {
-		dst_hold(tp->dst);
-		sk_setup_caps(sk, tp->dst);
-	}
-	rcu_read_unlock();
 	/* pack up chunks */
 	pkt_count = sctp_packet_pack(packet, head, gso, gfp);
 	if (!pkt_count) {
diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index 3fd06a2..5cb1aa5 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1135,6 +1135,7 @@ static void sctp_outq_flush_data(struct sctp_flush_ctx *ctx,
 static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
+	struct sock *sk = ctx->asoc->;
 	struct list_head *ltransport;
 	struct sctp_packet *packet;
 	struct sctp_transport *t;
@@ -1144,6 +1145,12 @@ static void sctp_outq_flush_transports(struct sctp_flush_ctx *ctx)
 		t = list_entry(ltransport, struct sctp_transport, send_ready);
 		packet = &t->packet;
 		if (!sctp_packet_empty(packet)) {
+			rcu_read_lock();
+			if (t->dst && __sk_dst_get(sk) != t->dst) {
+				dst_hold(t->dst);
+				sk_setup_caps(sk, t->dst);
+			}
+			rcu_read_unlock();
 			error = sctp_packet_transmit(packet, ctx->gfp);
 			if (error < 0)
 				ctx->q->asoc->>sk_err = -error;

             reply	other threads:[~2021-03-19  3:53 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-19  3:52 Xin Long [this message]
2021-03-19 18:40 ` [PATCH] sctp: move sk_route_caps check and set into sctp_outq_flush_transports patchwork-bot+netdevbpf

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