Merge branch 'mptcp-misc-fixes-for-v7-3-rc4'

Matthieu Baerts says:

====================
mptcp: misc fixes for v7.3-rc4

Here are two unrelated fixes:

- Patch 1: avoid unneeded actions on subflow reset. A fix for another
  fix introduced in v6.12 and targeting a commit from v5.7.

- Patch 2: close a possible race when scheduling a closing path. A fix
  for another fix introduced in v6.0 and targeting v5.10.

- Patch 3: fix bad accounting when __subflow_push_pending returns an
  error. A fix for v6.6.
====================

Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-0-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 20 insertions, 5 deletions

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8dc25ef1542c..e89a69ab927c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -856,12 +856,12 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 				mptcp_dss_corruption(msk, ssk);
 			}
 		} else {
+			sk_eat_skb(ssk, skb);
+
 			if (unlikely(!fin)) {
 				DEBUG_NET_WARN_ON_ONCE(1);
 				mptcp_dss_corruption(msk, ssk);
 			}
-
-			sk_eat_skb(ssk, skb);
 		}
 
 		WRITE_ONCE(tp->copied_seq, seq);
@@ -1664,7 +1664,9 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 
 static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
 {
-	tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
+	if (info->mss_now)
+		tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle,
+			 info->size_goal);
 	release_sock(ssk);
 }
 
@@ -1852,7 +1854,8 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
 			ret = __subflow_push_pending(sk, ssk, &info);
 			if (ret <= 0)
 				keep_pushing = false;
-			copied += ret;
+			else
+				copied += ret;
 		}
 
 		mptcp_for_each_subflow(msk, subflow) {
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 2b4c27426477..0384d6a023f9 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -585,7 +585,8 @@ struct mptcp_subflow_context {
 		is_mptfo : 1,	    /* subflow is doing TFO */
 		close_event_done : 1,       /* has done the post-closed part */
 		mpc_drop : 1,	    /* the MPC option has been dropped in a rtx */
-		__unused : 9;
+		resetting : 1,	    /* subflow is resetting */
+		__unused : 8;
 	bool	data_avail;
 	bool	scheduled;
 	bool	pm_listener;	    /* a listener managed by the kernel PM? */
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 01db7edce18a..f0a6725d2c37 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -438,6 +438,10 @@ void mptcp_subflow_reset(struct sock *ssk)
 	/* must hold: tcp_done() could drop last reference on parent */
 	sock_hold(sk);
 
+	subflow->resetting = 1;
+
+	/* No need to delay the actual close for to-be discarded data. */
+	__skb_queue_purge(&ssk->sk_receive_queue);
 	mptcp_send_active_reset_reason(ssk);
 	tcp_done(ssk);
 	if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags))
@@ -1883,6 +1887,13 @@ static void subflow_state_change(struct sock *sk)
 
 	__subflow_state_change(sk);
 
+	/* Rx queue processing is unneeded, error reporting will take place at
+	 * __mptcp_close_ssk() time and subflow reset can't happen in case of
+	 * fallback: subflow_sched_work_if_closed() would be a no-op.
+	 */
+	if (subflow->resetting)
+		return;
+
 	/* as recvmsg() does not acquire the subflow socket for ssk selection
 	 * a fin packet carrying a DSS can be unnoticed if we don't trigger
 	 * the data available machinery here.