Merge branch 'mptcp-fixes-for-6-4'

Matthieu Baerts says:

====================
mptcp: fixes for 6.4

Patch 1 correctly handles disconnect() failures that can happen in some
specific cases: now the socket state is set as unconnected as expected.
That fixes an issue introduced in v6.2.

Patch 2 fixes a divide by zero bug in mptcp_recvmsg() with a fix similar
to a recent one from Eric Dumazet for TCP introducing sk_wait_pending
flag. It should address an issue present in MPTCP from almost the
beginning, from v5.9.

Patch 3 fixes a possible list corruption on passive MPJ even if the race
seems very unlikely, better be safe than sorry. The possible issue is
present from v5.17.

Patch 4 consolidates fallback and non fallback state machines to avoid
leaking some MPTCP sockets. The fix is likely needed for versions from
v5.11.

Patch 5 drops code that is no longer used after the introduction of
patch 4/6. This is not really a fix but this patch can probably land in
the -net tree as well not to leave unused code.

Patch 6 ensures listeners are unhashed before updating their sk status
to avoid possible deadlocks when diag info are going to be retrieved
with a lock. Even if it should not be visible with the way we are
currently getting diag info, the issue is present from v5.17.
====================

Link: https://lore.kernel.org/r/20230620-upstream-net-20230620-misc-fixes-for-v6-4-v1-0-f36aa5eae8b9@tessares.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -1047,6 +1047,7 @@ static int mptcp_pm_nl_create_listen_socket(struct sock *sk,
 	if (err)
 		return err;
 
+	inet_sk_state_store(newsk, TCP_LISTEN);
 	err = kernel_listen(ssock, backlog);
 	if (err)
 		return err;

net/mptcp/protocol.h

@@ -113,7 +113,6 @@
 /* MPTCP socket atomic flags */
 #define MPTCP_NOSPACE		1
 #define MPTCP_WORK_RTX		2
-#define MPTCP_WORK_EOF		3
 #define MPTCP_FALLBACK_DONE	4
 #define MPTCP_WORK_CLOSE_SUBFLOW 5
 
@@ -476,14 +475,13 @@ struct mptcp_subflow_context {
 		send_mp_fail : 1,
 		send_fastclose : 1,
 		send_infinite_map : 1,
-		rx_eof : 1,
 		remote_key_valid : 1,        /* received the peer key from */
 		disposable : 1,	    /* ctx can be free at ulp release time */
 		stale : 1,	    /* unable to snd/rcv data, do not use for xmit */
 		local_id_valid : 1, /* local_id is correctly initialized */
 		valid_csum_seen : 1,        /* at least one csum validated */
 		is_mptfo : 1,	    /* subflow is doing TFO */
-		__unused : 8;
+		__unused : 9;
 	enum mptcp_data_avail data_avail;
 	u32	remote_nonce;
 	u64	thmac;
@@ -720,7 +718,6 @@ static inline u64 mptcp_expand_seq(u64 old_seq, u64 cur_seq, bool use_64bit)
 void __mptcp_check_push(struct sock *sk, struct sock *ssk);
 void __mptcp_data_acked(struct sock *sk);
 void __mptcp_error_report(struct sock *sk);
-void mptcp_subflow_eof(struct sock *sk);
 bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit);
 static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk)
 {

net/mptcp/subflow.c

@@ -1749,14 +1749,16 @@ static void subflow_state_change(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct sock *parent = subflow->conn;
+	struct mptcp_sock *msk;
 
 	__subflow_state_change(sk);
 
+	msk = mptcp_sk(parent);
 	if (subflow_simultaneous_connect(sk)) {
 		mptcp_propagate_sndbuf(parent, sk);
 		mptcp_do_fallback(sk);
-		mptcp_rcv_space_init(mptcp_sk(parent), sk);
-		pr_fallback(mptcp_sk(parent));
+		mptcp_rcv_space_init(msk, sk);
+		pr_fallback(msk);
 		subflow->conn_finished = 1;
 		mptcp_set_connected(parent);
 	}
@@ -1772,11 +1774,12 @@ static void subflow_state_change(struct sock *sk)
 
 	subflow_sched_work_if_closed(mptcp_sk(parent), sk);
 
-	if (__mptcp_check_fallback(mptcp_sk(parent)) &&
-	    !subflow->rx_eof && subflow_is_done(sk)) {
-		subflow->rx_eof = 1;
-		mptcp_subflow_eof(parent);
-	}
+	/* when the fallback subflow closes the rx side, trigger a 'dummy'
+	 * ingress data fin, so that the msk state will follow along
+	 */
+	if (__mptcp_check_fallback(msk) && subflow_is_done(sk) && msk->first == sk &&
+	    mptcp_update_rcv_data_fin(msk, READ_ONCE(msk->ack_seq), true))
+		mptcp_schedule_work(parent);
 }
 
 void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)