Merge branch 'mptcp-a-bunch-of-fixes'

Paolo Abeni says:

====================
mptcp: a bunch of fixes

This series bundle a few MPTCP fixes for the current net tree.
They have been detected via syzkaller and packetdrill

Patch 1 fixes a slow close for orphaned sockets

Patch 2 fixes another hangup at close time, when no
data was actually transmitted before close

Patch 3 fixes a memory leak with unusual sockopts

Patch 4 fixes stray wake-ups on listener sockets
====================

Link: https://lore.kernel.org/r/cover.1613755058.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/options.c

@@ -411,6 +411,7 @@ static void clear_3rdack_retransmission(struct sock *sk)
 }
 
 static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
+					 bool snd_data_fin_enable,
 					 unsigned int *size,
 					 unsigned int remaining,
 					 struct mptcp_out_options *opts)
@@ -428,9 +429,10 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 	if (!skb)
 		return false;
 
-	/* MPC/MPJ needed only on 3rd ack packet */
-	if (subflow->fully_established ||
-	    subflow->snd_isn != TCP_SKB_CB(skb)->seq)
+	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
+	if (subflow->fully_established || snd_data_fin_enable ||
+	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
+	    sk->sk_state != TCP_ESTABLISHED)
 		return false;
 
 	if (subflow->mp_capable) {
@@ -502,20 +504,20 @@ static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 }
 
 static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
+					  bool snd_data_fin_enable,
 					  unsigned int *size,
 					  unsigned int remaining,
 					  struct mptcp_out_options *opts)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
-	u64 snd_data_fin_enable, ack_seq;
 	unsigned int dss_size = 0;
 	struct mptcp_ext *mpext;
 	unsigned int ack_size;
 	bool ret = false;
+	u64 ack_seq;
 
 	mpext = skb ? mptcp_get_ext(skb) : NULL;
-	snd_data_fin_enable = mptcp_data_fin_enabled(msk);
 
 	if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 		unsigned int map_size;
@@ -717,12 +719,15 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 			       unsigned int *size, unsigned int remaining,
 			       struct mptcp_out_options *opts)
 {
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	unsigned int opt_size = 0;
+	bool snd_data_fin;
 	bool ret = false;
 
 	opts->suboptions = 0;
 
-	if (unlikely(mptcp_check_fallback(sk)))
+	if (unlikely(__mptcp_check_fallback(msk)))
 		return false;
 
 	/* prevent adding of any MPTCP related options on reset packet
@@ -731,10 +736,10 @@ bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 	if (unlikely(skb && TCP_SKB_CB(skb)->tcp_flags & TCPHDR_RST))
 		return false;
 
-	if (mptcp_established_options_mp(sk, skb, &opt_size, remaining, opts))
+	snd_data_fin = mptcp_data_fin_enabled(msk);
+	if (mptcp_established_options_mp(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 		ret = true;
-	else if (mptcp_established_options_dss(sk, skb, &opt_size, remaining,
-					       opts))
+	else if (mptcp_established_options_dss(sk, skb, snd_data_fin, &opt_size, remaining, opts))
 		ret = true;
 
 	/* we reserved enough space for the above options, and exceeding the

net/mptcp/protocol.c

@@ -11,6 +11,7 @@
 #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>
@@ -19,6 +20,7 @@
 #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>
@@ -2264,13 +2266,12 @@ static void mptcp_worker(struct work_struct *work)
 	__mptcp_check_send_data_fin(sk);
 	mptcp_check_data_fin(sk);
 
-	/* if the msk data is completely acked, or the socket timedout,
-	 * there is no point in keeping around an orphaned sk
+	/* There is no point in keeping around an orphaned sk timedout or
+	 * closed, but we need the msk around to reply to incoming DATA_FIN,
+	 * even if it is orphaned and in FIN_WAIT2 state
 	 */
 	if (sock_flag(sk, SOCK_DEAD) &&
-	    (mptcp_check_close_timeout(sk) ||
-	    (state != sk->sk_state &&
-	    ((1 << inet_sk_state_load(sk)) & (TCPF_CLOSE | TCPF_FIN_WAIT2))))) {
+	    (mptcp_check_close_timeout(sk) || sk->sk_state == TCP_CLOSE)) {
 		inet_sk_state_store(sk, TCP_CLOSE);
 		__mptcp_destroy_sock(sk);
 		goto unlock;
@@ -3375,10 +3376,34 @@ 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	   = inet_release,
+	.release	   = mptcp_release,
 	.bind		   = mptcp_bind,
 	.connect	   = mptcp_stream_connect,
 	.socketpair	   = sock_no_socketpair,
@@ -3470,10 +3495,35 @@ 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	   = inet6_release,
+	.release	   = mptcp6_release,
 	.bind		   = mptcp_bind,
 	.connect	   = mptcp_stream_connect,
 	.socketpair	   = sock_no_socketpair,

net/mptcp/subflow.c

@@ -1096,6 +1096,12 @@ static void subflow_data_ready(struct sock *sk)
 
 	msk = mptcp_sk(parent);
 	if (state & TCPF_LISTEN) {
+		/* MPJ subflow are removed from accept queue before reaching here,
+		 * avoid stray wakeups
+		 */
+		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
+			return;
+
 		set_bit(MPTCP_DATA_READY, &msk->flags);
 		parent->sk_data_ready(parent);
 		return;