[PATCH net v2 0/3] mptcp: misc fixes for v7.3-rc4

[PATCH net v2 0/3] mptcp: misc fixes for v7.3-rc4

[Matthieu Baerts (NGI0)]

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.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Changes in v2:
- Patch 1: rewording commit msg & consume skb and purge queue early.
- Patch 3: new, for an issue spot by Clashiko.
- Link to v1: https://patch.msgid.link/20260915-net-mptcp-misc-fixes-7-3-rc4-v1-0-a257797dd5d0@kernel.org

---
Paolo Abeni (3):
      mptcp: avoid unneeded actions on subflow reset
      mptcp: close race between scheduler and state change
      mptcp: fix bad accounting in __mptcp_subflow_push_pending()

 net/mptcp/protocol.c | 11 +++++++----
 net/mptcp/protocol.h |  3 ++-
 net/mptcp/subflow.c  | 11 +++++++++++
 3 files changed, 20 insertions(+), 5 deletions(-)
---
base-commit: 9ca4ba24259183ce15665be86b2956cd896c4687
change-id: 20260915-net-mptcp-misc-fixes-7-3-rc4-538b9d7ec047

Best regards,
--  
Matthieu Baerts (NGI0) <matttbe@kernel.org>

[PATCH net v2 1/3] mptcp: avoid unneeded actions on subflow reset

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

Once in a blue moon, the mptcp receive path can recursively call
mptcp_data_ready() via state change under unlucky error conditions, and
then try to hold the data lock again.

Break the recursion loop explicitly checking for the exceptional
condition.

Add a new flag instead of using an existing one like 'closing', to exit
early in subflow_state_change(), and explicitly flush the RX queue at
reset time.

This avoids unneeded processing to check for available data -- calling
get_mapping_status() and more on a dying subflow -- but also in error
reporting and worker scheduling.

Note that we must consume the currently peeked skb before invoking
mptcp_dss_corruption to avoid consuming it again after the eventual
reset has freed it.

Fixes: e32d262c89e2 ("mptcp: handle consistently DSS corruption")
Cc: stable@vger.kernel.org
Reported-by: Xinyang Ge <xinyang@anthropic.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
v2:
 - rewording to please Clashiko
 - consume skb before dss_corruption, and purge queue during reset
---
 net/mptcp/protocol.c |  4 ++--
 net/mptcp/protocol.h |  3 ++-
 net/mptcp/subflow.c  | 11 +++++++++++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8dc25ef1542c..d9fc3be9d2db 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);
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.

-- 
2.55.0

[PATCH net v2 2/3] mptcp: close race between scheduler and state change

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

The mptcp scheduler may race with subflow sockets state change: data
transmission on the selected socket may fail and a later release could
try to use mss_now reset to 0 for a divide operation.

Address the issue by explicitly checking for the critical scenario.

Fixes: c886d70286bf ("mptcp: do not queue data on closed subflows")
Cc: stable@vger.kernel.org
Reported-by: Shardul Bankar <shardul.b@mpiricsoftware.com>
Reported-by: Xinyang Ge <xinyang@anthropic.com>
Closes: https://lore.kernel.org/20260525194828.1137119-1-shardul.b@mpiricsoftware.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d9fc3be9d2db..577d0134b9ec 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -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);
 }
 

-- 
2.55.0

[PATCH net v2 3/3] mptcp: fix bad accounting in __mptcp_subflow_push_pending()

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

If __subflow_push_pending() errors out we should avoid updating the
copied byte counters, to avoid mismatch push call later on.

Fixes: 0fa1b3783a17 ("mptcp: use get_send wrapper")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 577d0134b9ec..e89a69ab927c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1854,7 +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) {

-- 
2.55.0

Re: [PATCH net v2 0/3] mptcp: misc fixes for v7.3-rc4

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 17 Sep 2026 15:05:56 +0200 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net,v2,1/3] mptcp: avoid unneeded actions on subflow reset
    https://git.kernel.org/netdev/net/c/2b0f561f21b2
  - [net,v2,2/3] mptcp: close race between scheduler and state change
    https://git.kernel.org/netdev/net/c/42064de57fb8
  - [net,v2,3/3] mptcp: fix bad accounting in __mptcp_subflow_push_pending()
    https://git.kernel.org/netdev/net/c/f3ef03357396

You are awesome, thank you!
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