[PATCH net 4/5] mptcp: fix setsockopt(IP_TOS) subflow locking

[Matthieu Baerts]

From: Paolo Abeni <pabeni@xxxxxxxxxx>

The MPTCP implementation of the IP_TOS socket option uses the lockless
variant of the TOS manipulation helper and does not hold such lock at
the helper invocation time.

Add the required locking.

Fixes: ffcacff87cd6 ("mptcp: Support for IP_TOS for MPTCP setsockopt()")
Cc: stable@xxxxxxxxxxxxxxx
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/457
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matttbe@xxxxxxxxxx>
---
 net/mptcp/sockopt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index 77f5e8932abf..353680733700 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -738,8 +738,11 @@ static int mptcp_setsockopt_v4_set_tos(struct mptcp_sock *msk, int optname,
 	val = READ_ONCE(inet_sk(sk)->tos);
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+		bool slow;
 
+		slow = lock_sock_fast(ssk);
 		__ip_sock_set_tos(ssk, val);
+		unlock_sock_fast(ssk, slow);
 	}
 	release_sock(sk);
 

-- 
2.40.1