Merge branch 'mptcp-various-bugfixes-and-improvements'

Florian Westphal says:

====================
mptcp: various bugfixes and improvements

This series contains the following mptcp bug fixes:

1. Fix crash on tcp fallback when userspace doesn't provide a 'struct
   sockaddr' to accept().
2. Close mptcp socket only when all subflows have closed, not just the first.
3. avoid stream data corruption when we'd receive identical mapping at the
    exact same time on multiple subflows.
4. Fix "fn parameter not described" kerneldoc warnings.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

@@ -57,10 +57,43 @@ static bool __mptcp_needs_tcp_fallback(const struct mptcp_sock *msk)
 	return msk->first && !sk_is_mptcp(msk->first);
 }
 
+static struct socket *mptcp_is_tcpsk(struct sock *sk)
+{
+	struct socket *sock = sk->sk_socket;
+
+	if (sock->sk != sk)
+		return NULL;
+
+	if (unlikely(sk->sk_prot == &tcp_prot)) {
+		/* we are being invoked after mptcp_accept() has
+		 * accepted a non-mp-capable flow: sk is a tcp_sk,
+		 * not an mptcp one.
+		 *
+		 * Hand the socket over to tcp so all further socket ops
+		 * bypass mptcp.
+		 */
+		sock->ops = &inet_stream_ops;
+		return sock;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
+		sock->ops = &inet6_stream_ops;
+		return sock;
+#endif
+	}
+
+	return NULL;
+}
+
 static struct socket *__mptcp_tcp_fallback(struct mptcp_sock *msk)
 {
+	struct socket *sock;
+
 	sock_owned_by_me((const struct sock *)msk);
 
+	sock = mptcp_is_tcpsk((struct sock *)msk);
+	if (unlikely(sock))
+		return sock;
+
 	if (likely(!__mptcp_needs_tcp_fallback(msk)))
 		return NULL;
 
@@ -84,6 +117,10 @@ static struct socket *__mptcp_socket_create(struct mptcp_sock *msk, int state)
 	struct socket *ssock;
 	int err;
 
+	ssock = __mptcp_tcp_fallback(msk);
+	if (unlikely(ssock))
+		return ssock;
+
 	ssock = __mptcp_nmpc_socket(msk);
 	if (ssock)
 		goto set_state;
@@ -121,6 +158,27 @@ static void __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
 	MPTCP_SKB_CB(skb)->offset = offset;
 }
 
+/* both sockets must be locked */
+static bool mptcp_subflow_dsn_valid(const struct mptcp_sock *msk,
+				    struct sock *ssk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	u64 dsn = mptcp_subflow_get_mapped_dsn(subflow);
+
+	/* revalidate data sequence number.
+	 *
+	 * mptcp_subflow_data_available() is usually called
+	 * without msk lock.  Its unlikely (but possible)
+	 * that msk->ack_seq has been advanced since the last
+	 * call found in-sequence data.
+	 */
+	if (likely(dsn == msk->ack_seq))
+		return true;
+
+	subflow->data_avail = 0;
+	return mptcp_subflow_data_available(ssk);
+}
+
 static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 					   struct sock *ssk,
 					   unsigned int *bytes)
@@ -132,6 +190,11 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 	struct tcp_sock *tp;
 	bool done = false;
 
+	if (!mptcp_subflow_dsn_valid(msk, ssk)) {
+		*bytes = 0;
+		return false;
+	}
+
 	if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
 		int rcvbuf = max(ssk->sk_rcvbuf, sk->sk_rcvbuf);
 
@@ -290,6 +353,15 @@ void mptcp_data_acked(struct sock *sk)
 		sock_hold(sk);
 }
 
+void mptcp_subflow_eof(struct sock *sk)
+{
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	if (!test_and_set_bit(MPTCP_WORK_EOF, &msk->flags) &&
+	    schedule_work(&msk->work))
+		sock_hold(sk);
+}
+
 static void mptcp_stop_timer(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -994,6 +1066,27 @@ static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)
 	return 0;
 }
 
+static void mptcp_check_for_eof(struct mptcp_sock *msk)
+{
+	struct mptcp_subflow_context *subflow;
+	struct sock *sk = (struct sock *)msk;
+	int receivers = 0;
+
+	mptcp_for_each_subflow(msk, subflow)
+		receivers += !subflow->rx_eof;
+
+	if (!receivers && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
+		/* hopefully temporary hack: propagate shutdown status
+		 * to msk, when all subflows agree on it
+		 */
+		sk->sk_shutdown |= RCV_SHUTDOWN;
+
+		smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
+		set_bit(MPTCP_DATA_READY, &msk->flags);
+		sk->sk_data_ready(sk);
+	}
+}
+
 static void mptcp_worker(struct work_struct *work)
 {
 	struct mptcp_sock *msk = container_of(work, struct mptcp_sock, work);
@@ -1010,6 +1103,9 @@ static void mptcp_worker(struct work_struct *work)
 	__mptcp_flush_join_list(msk);
 	__mptcp_move_skbs(msk);
 
+	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))
+		mptcp_check_for_eof(msk);
+
 	if (!test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))
 		goto unlock;
 
@@ -1752,7 +1848,9 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 
 	msk = mptcp_sk(sk);
 	lock_sock(sk);
-	ssock = __mptcp_nmpc_socket(msk);
+	ssock = __mptcp_tcp_fallback(msk);
+	if (!ssock)
+		ssock = __mptcp_nmpc_socket(msk);
 	if (ssock) {
 		mask = ssock->ops->poll(file, ssock, wait);
 		release_sock(sk);
@@ -1762,9 +1860,6 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
 	release_sock(sk);
 	sock_poll_wait(file, sock, wait);
 	lock_sock(sk);
-	ssock = __mptcp_tcp_fallback(msk);
-	if (unlikely(ssock))
-		return ssock->ops->poll(file, ssock, NULL);
 
 	if (test_bit(MPTCP_DATA_READY, &msk->flags))
 		mask = EPOLLIN | EPOLLRDNORM;
@@ -1783,11 +1878,17 @@ static int mptcp_shutdown(struct socket *sock, int how)
 {
 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
 	struct mptcp_subflow_context *subflow;
+	struct socket *ssock;
 	int ret = 0;
 
 	pr_debug("sk=%p, how=%d", msk, how);
 
 	lock_sock(sock->sk);
+	ssock = __mptcp_tcp_fallback(msk);
+	if (ssock) {
+		release_sock(sock->sk);
+		return inet_shutdown(ssock, how);
+	}
 
 	if (how == SHUT_WR || how == SHUT_RDWR)
 		inet_sk_state_store(sock->sk, TCP_FIN_WAIT1);

net/mptcp/protocol.h

@@ -89,6 +89,7 @@
 #define MPTCP_DATA_READY	0
 #define MPTCP_SEND_SPACE	1
 #define MPTCP_WORK_RTX		2
+#define MPTCP_WORK_EOF		3
 
 static inline __be32 mptcp_option(u8 subopt, u8 len, u8 nib, u8 field)
 {
@@ -339,6 +340,7 @@ void mptcp_finish_connect(struct sock *sk);
 void mptcp_data_ready(struct sock *sk, struct sock *ssk);
 bool mptcp_finish_join(struct sock *sk);
 void mptcp_data_acked(struct sock *sk);
+void mptcp_subflow_eof(struct sock *sk);
 
 int mptcp_token_new_request(struct request_sock *req);
 void mptcp_token_destroy_request(u32 token);

net/mptcp/subflow.c

@@ -994,8 +994,7 @@ static void subflow_state_change(struct sock *sk)
 	if (!(parent->sk_shutdown & RCV_SHUTDOWN) &&
 	    !subflow->rx_eof && subflow_is_done(sk)) {
 		subflow->rx_eof = 1;
-		parent->sk_shutdown |= RCV_SHUTDOWN;
-		__subflow_state_change(parent);
+		mptcp_subflow_eof(parent);
 	}
 }
 

net/mptcp/token.c

@@ -40,7 +40,7 @@ static int token_used __read_mostly;
 
 /**
  * mptcp_token_new_request - create new key/idsn/token for subflow_request
- * @req - the request socket
+ * @req: the request socket
  *
  * This function is called when a new mptcp connection is coming in.
  *
@@ -80,7 +80,7 @@ int mptcp_token_new_request(struct request_sock *req)
 
 /**
  * mptcp_token_new_connect - create new key/idsn/token for subflow
- * @sk - the socket that will initiate a connection
+ * @sk: the socket that will initiate a connection
  *
  * This function is called when a new outgoing mptcp connection is
  * initiated.
@@ -125,6 +125,7 @@ int mptcp_token_new_connect(struct sock *sk)
 /**
  * mptcp_token_new_accept - insert token for later processing
  * @token: the token to insert to the tree
+ * @conn: the just cloned socket linked to the new connection
  *
  * Called when a SYN packet creates a new logical connection, i.e.
  * is not a join request.
@@ -169,7 +170,7 @@ struct mptcp_sock *mptcp_token_get_sock(u32 token)
 
 /**
  * mptcp_token_destroy_request - remove mptcp connection/token
- * @token - token of mptcp connection to remove
+ * @token: token of mptcp connection to remove
  *
  * Remove not-yet-fully-established incoming connection identified
  * by @token.
@@ -183,7 +184,7 @@ void mptcp_token_destroy_request(u32 token)
 
 /**
  * mptcp_token_destroy - remove mptcp connection/token
- * @token - token of mptcp connection to remove
+ * @token: token of mptcp connection to remove
  *
  * Remove the connection identified by @token.
  */