mptcp: revert "mptcp: provide subflow aware release function"

This change reverts commit ad98dd37051e ("mptcp: provide subflow aware
release function"). The latter introduced a deadlock spotted by
syzkaller and is not needed anymore after the previous commit.

Fixes: ad98dd37051e ("mptcp: provide subflow aware release function")
Signed-off-by: Paolo Abeni <[e-mail]>
Reviewed-by: Mat Martineau <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/mptcp/protocol.c

···
 #include <linux/netdevice.h>
 #include <linux/sched/signal.h>
 #include <linux/atomic.h>
-#include <linux/igmp.h>
 #include <net/sock.h>
 #include <net/inet_common.h>
 #include <net/inet_hashtables.h>
···
 #include <net/tcp_states.h>
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 #include <net/transp_v6.h>
-#include <net/addrconf.h>
 #endif
 #include <net/mptcp.h>
 #include <net/xfrm.h>
···
 	return mask;
 }
 
-static int mptcp_release(struct socket *sock)
-{
-	struct mptcp_subflow_context *subflow;
-	struct sock *sk = sock->sk;
-	struct mptcp_sock *msk;
-
-	if (!sk)
-		return 0;
-
-	lock_sock(sk);
-
-	msk = mptcp_sk(sk);
-
-	mptcp_for_each_subflow(msk, subflow) {
-		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-
-		ip_mc_drop_socket(ssk);
-	}
-
-	release_sock(sk);
-
-	return inet_release(sock);
-}
-
 static const struct proto_ops mptcp_stream_ops = {
 	.family		   = PF_INET,
 	.owner		   = THIS_MODULE,
-	.release	   = mptcp_release,
+	.release	   = inet_release,
 	.bind		   = mptcp_bind,
 	.connect	   = mptcp_stream_connect,
 	.socketpair	   = sock_no_socketpair,
···
 }
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
-static int mptcp6_release(struct socket *sock)
-{
-	struct mptcp_subflow_context *subflow;
-	struct mptcp_sock *msk;
-	struct sock *sk = sock->sk;
-
-	if (!sk)
-		return 0;
-
-	lock_sock(sk);
-
-	msk = mptcp_sk(sk);
-
-	mptcp_for_each_subflow(msk, subflow) {
-		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-
-		ip_mc_drop_socket(ssk);
-		ipv6_sock_mc_close(ssk);
-		ipv6_sock_ac_close(ssk);
-	}
-
-	release_sock(sk);
-	return inet6_release(sock);
-}
-
 static const struct proto_ops mptcp_v6_stream_ops = {
 	.family		   = PF_INET6,
 	.owner		   = THIS_MODULE,
-	.release	   = mptcp6_release,
+	.release	   = inet6_release,
 	.bind		   = mptcp_bind,
 	.connect	   = mptcp_stream_connect,
 	.socketpair	   = sock_no_socketpair,