From: Xin Long <lucien.xin@gmail.com>
Date: Mon, 15 Jan 2018 17:01:19 +0800
Subject: sctp: reinit stream if stream outcnt has been change by sinit in sendmsg
Patch-mainline: v4.15-rc9
Git-commit: 625637bf4afa45204bd87e4218645182a919485a
References: bsc#1076830

After introducing sctp_stream structure, sctp uses stream->outcnt as the
out stream nums instead of c.sinit_num_ostreams.

However when users use sinit in cmsg, it only updates c.sinit_num_ostreams
in sctp_sendmsg. At that moment, stream->outcnt is still using previous
value. If it's value is not updated, the sinit_num_ostreams of sinit could
not really work.

This patch is to fix it by updating stream->outcnt and reiniting stream
if stream outcnt has been change by sinit in sendmsg.

Fixes: a83863174a61 ("sctp: prepare asoc stream for stream reconf")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/sctp/socket.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 9949c8c50b17..f2f437867b55 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1850,8 +1850,13 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len)
 		 */
 		if (sinit) {
 			if (sinit->sinit_num_ostreams) {
-				asoc->c.sinit_num_ostreams =
-					sinit->sinit_num_ostreams;
+				__u16 outcnt = sinit->sinit_num_ostreams;
+
+				asoc->c.sinit_num_ostreams = outcnt;
+				/* outcnt has been changed, so re-init stream */
+				err = sctp_stream_init(asoc, GFP_KERNEL);
+				if (err)
+					goto out_free;
 			}
 			if (sinit->sinit_max_instreams) {
 				asoc->c.sinit_max_instreams =
-- 
2.16.1