Merge branch 'mptcp-deadlock'

Paolo Abeni says:

====================
mptcp: mptcp: fix deadlock in mptcp{,6}_release

syzkaller has reported a few deadlock triggered by
mptcp{,6}_release.

These patches address the issue in the easy way - blocking
the relevant, multicast related, sockopt options on MPTCP
sockets.

Note that later on net-next we are going to revert patch 1/2,
as a part of a larger MPTCP sockopt implementation refactor
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

@@ -11,7 +11,6 @@
 #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>
@@ -20,7 +19,6 @@
 #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>
@@ -2878,6 +2876,48 @@ static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
 	return ret;
 }
 
+static bool mptcp_unsupported(int level, int optname)
+{
+	if (level == SOL_IP) {
+		switch (optname) {
+		case IP_ADD_MEMBERSHIP:
+		case IP_ADD_SOURCE_MEMBERSHIP:
+		case IP_DROP_MEMBERSHIP:
+		case IP_DROP_SOURCE_MEMBERSHIP:
+		case IP_BLOCK_SOURCE:
+		case IP_UNBLOCK_SOURCE:
+		case MCAST_JOIN_GROUP:
+		case MCAST_LEAVE_GROUP:
+		case MCAST_JOIN_SOURCE_GROUP:
+		case MCAST_LEAVE_SOURCE_GROUP:
+		case MCAST_BLOCK_SOURCE:
+		case MCAST_UNBLOCK_SOURCE:
+		case MCAST_MSFILTER:
+			return true;
+		}
+		return false;
+	}
+	if (level == SOL_IPV6) {
+		switch (optname) {
+		case IPV6_ADDRFORM:
+		case IPV6_ADD_MEMBERSHIP:
+		case IPV6_DROP_MEMBERSHIP:
+		case IPV6_JOIN_ANYCAST:
+		case IPV6_LEAVE_ANYCAST:
+		case MCAST_JOIN_GROUP:
+		case MCAST_LEAVE_GROUP:
+		case MCAST_JOIN_SOURCE_GROUP:
+		case MCAST_LEAVE_SOURCE_GROUP:
+		case MCAST_BLOCK_SOURCE:
+		case MCAST_UNBLOCK_SOURCE:
+		case MCAST_MSFILTER:
+			return true;
+		}
+		return false;
+	}
+	return false;
+}
+
 static int mptcp_setsockopt(struct sock *sk, int level, int optname,
 			    sockptr_t optval, unsigned int optlen)
 {
@@ -2886,6 +2926,9 @@ static int mptcp_setsockopt(struct sock *sk, int level, int optname,
 
 	pr_debug("msk=%p", msk);
 
+	if (mptcp_unsupported(level, optname))
+		return -ENOPROTOOPT;
+
 	if (level == SOL_SOCKET)
 		return mptcp_setsockopt_sol_socket(msk, optname, optval, optlen);
 
@@ -3419,34 +3462,10 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 	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,
@@ -3538,35 +3557,10 @@ void __init mptcp_proto_init(void)
 }
 
 #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,