[PATCH 6.12.y 0/5] mptcp: fix recent failed backports (20260919)

[PATCH 6.12.y 0/5] mptcp: fix recent failed backports (20260919)

[Matthieu Baerts (NGI0)]

The following patches could not be applied without conflicts in this
tree:

- 2b0f561f21b2 ("mptcp: avoid unneeded actions on subflow reset")
- 42064de57fb8 ("mptcp: close race between scheduler and state change")
- f3ef03357396 ("mptcp: fix bad accounting in __mptcp_subflow_push_pending()")

I backported the following commits to avoid conflicts:

- 581c8cbfa934 ("mptcp: annotate data-races around subflow->fully_established")
- caa4a79f74f3 ("mptcp: remove unneeded READ_ONCE() annotation")

Conflicts (if any) have been resolved, and documented in each patch.

Gang Yan (1):
  mptcp: annotate data-races around subflow->fully_established

Paolo Abeni (4):
  mptcp: remove unneeded READ_ONCE() annotation
  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 | 13 ++++++++-----
 net/mptcp/protocol.h |  1 +
 net/mptcp/subflow.c  | 11 +++++++++++
 3 files changed, 20 insertions(+), 5 deletions(-)

-- 
2.55.0

[PATCH 6.12.y 1/5] mptcp: annotate data-races around subflow->fully_established

[Matthieu Baerts (NGI0)]

From: Gang Yan <yangang@kylinos.cn>

commit 581c8cbfa934aaa555daa4e843242fcecc160f05 upstream.

We introduce the same handling for potential data races with the
'fully_established' flag in subflow as previously done for
msk->fully_established.

Additionally, we make a crucial change: convert the subflow's
'fully_established' from 'bit_field' to 'bool' type. This is
necessary because methods for avoiding data races don't work well
with 'bit_field'. Specifically, the 'READ_ONCE' needs to know
the size of the variable being accessed, which is not supported in
'bit_field'. Also, 'test_bit' expect the address of 'bit_field'.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/516
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20241021-net-next-mptcp-misc-6-13-v1-2-1ef02746504a@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 2b0f561f21b2 ("mptcp: avoid unneeded actions on subflow reset")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/options.c  | 4 ++--
 net/mptcp/protocol.c | 2 +-
 net/mptcp/protocol.h | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index d238dd374ce9..123c3691833f 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -532,7 +532,7 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 		return false;
 
 	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
-	if (subflow->fully_established || snd_data_fin_enable ||
+	if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||
 	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 	    sk->sk_state != TCP_ESTABLISHED)
 		return false;
@@ -999,7 +999,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	/* here we can process OoO, in-window pkts, only in-sequence 4th ack
 	 * will make the subflow fully established
 	 */
-	if (likely(subflow->fully_established)) {
+	if (likely(READ_ONCE(subflow->fully_established))) {
 		/* on passive sockets, check for 3rd ack retransmission
 		 * note that msk is always set by subflow_syn_recv_sock()
 		 * for mp_join subflows
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2f34e92d9cce..a4054ed24605 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3685,7 +3685,7 @@ static void schedule_3rdack_retransmission(struct sock *ssk)
 	struct tcp_sock *tp = tcp_sk(ssk);
 	unsigned long timeout;
 
-	if (mptcp_subflow_ctx(ssk)->fully_established)
+	if (READ_ONCE(mptcp_subflow_ctx(ssk)->fully_established))
 		return;
 
 	/* reschedule with a timeout above RTT, as we must look only for drop */
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 2ac28f6ddff5..cd4481c93b6d 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -545,7 +545,7 @@ 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 : 8;
+		__unused : 9;
 	bool	data_avail;
 	bool	scheduled;
 	bool	pm_listener;	    /* a listener managed by the kernel PM? */
-- 
2.55.0

Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    mptcp: annotate data-races around subflow->fully_established

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-annotate-data-races-around-subflow-fully_established.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-338598-greg=kroah.com@vger.kernel.org Sat Sep 19 21:57:10 2026
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 19 Sep 2026 21:56:44 +0200
Subject: mptcp: annotate data-races around subflow->fully_established
To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: Gang Yan <yangang@kylinos.cn>, sashal@kernel.org, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20260919195642.1977885-8-matttbe@kernel.org>

From: Gang Yan <yangang@kylinos.cn>

commit 581c8cbfa934aaa555daa4e843242fcecc160f05 upstream.

We introduce the same handling for potential data races with the
'fully_established' flag in subflow as previously done for
msk->fully_established.

Additionally, we make a crucial change: convert the subflow's
'fully_established' from 'bit_field' to 'bool' type. This is
necessary because methods for avoiding data races don't work well
with 'bit_field'. Specifically, the 'READ_ONCE' needs to know
the size of the variable being accessed, which is not supported in
'bit_field'. Also, 'test_bit' expect the address of 'bit_field'.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/516
Signed-off-by: Gang Yan <yangang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20241021-net-next-mptcp-misc-6-13-v1-2-1ef02746504a@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 2b0f561f21b2 ("mptcp: avoid unneeded actions on subflow reset")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/options.c  |    4 ++--
 net/mptcp/protocol.c |    2 +-
 net/mptcp/protocol.h |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -532,7 +532,7 @@ static bool mptcp_established_options_mp
 		return false;
 
 	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
-	if (subflow->fully_established || snd_data_fin_enable ||
+	if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||
 	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 	    sk->sk_state != TCP_ESTABLISHED)
 		return false;
@@ -999,7 +999,7 @@ static bool check_fully_established(stru
 	/* here we can process OoO, in-window pkts, only in-sequence 4th ack
 	 * will make the subflow fully established
 	 */
-	if (likely(subflow->fully_established)) {
+	if (likely(READ_ONCE(subflow->fully_established))) {
 		/* on passive sockets, check for 3rd ack retransmission
 		 * note that msk is always set by subflow_syn_recv_sock()
 		 * for mp_join subflows
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3685,7 +3685,7 @@ static void schedule_3rdack_retransmissi
 	struct tcp_sock *tp = tcp_sk(ssk);
 	unsigned long timeout;
 
-	if (mptcp_subflow_ctx(ssk)->fully_established)
+	if (READ_ONCE(mptcp_subflow_ctx(ssk)->fully_established))
 		return;
 
 	/* reschedule with a timeout above RTT, as we must look only for drop */
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -545,7 +545,7 @@ 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 : 8;
+		__unused : 9;
 	bool	data_avail;
 	bool	scheduled;
 	bool	pm_listener;	    /* a listener managed by the kernel PM? */


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-6.12/mptcp-annotate-data-races-around-subflow-fully_established.patch
queue-6.12/selftests-mptcp-fix-an-uaf-in-mptcp_connect.c.patch
queue-6.12/mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
queue-6.12/mptcp-syncookies-remember-the-request-backup-flag.patch
queue-6.12/mptcp-remove-unneeded-read_once-annotation.patch
queue-6.12/mptcp-close-race-between-scheduler-and-state-change.patch
queue-6.12/tcp-use-gfp_atomic-in-tcp_send_active_reset.patch
queue-6.12/mptcp-avoid-unneeded-actions-on-subflow-reset.patch
queue-6.12/mptcp-options-handle-mpc-data-csum-reqd-no-csum.patch
queue-6.12/mptcp-subflow-no-need-to-copy-thmac-during-ulp_clone.patch

Re: Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] mptcp: build failure due to READ_ONCE() on bit-field
--

commit 2cede4d0675228e6db5b209f56d2a298cf7cb2e9
Author: gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>
Subject: Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

This commit annotates data races around the fully_established flag in the
mptcp subflow context. It aims to convert the flag from a bit-field to a
boolean type to safely use READ_ONCE() and WRITE_ONCE().

Link: https://patch.msgid.link/20241021-net-next-mptcp-misc-6-13-v1-2-1ef02746504a@kernel.org

>     Additionally, we make a crucial change: convert the subflow's
>     'fully_established' from 'bit_field' to 'bool' type. This is
>     necessary because methods for avoiding data races don't work well
>     with 'bit_field'. Specifically, the 'READ_ONCE' needs to know
>     the size of the variable being accessed, which is not supported in
>     'bit_field'. Also, 'test_bit' expect the address of 'bit_field'.

[Severity: Low]
Was the hunk converting this field to a boolean dropped during the backport?
It appears fully_established is still defined as a bit-field in
struct mptcp_subflow_context.

Additionally, the write side update was missed in the backport:

net/mptcp/subflow.c:__mptcp_subflow_fully_established() {
    ...
	subflow->fully_established = 1;
    ...
}

This lacks the WRITE_ONCE() annotation and continues to perform an unsafe
read-modify-write on the shared bit-field word.

> diff --git a/net/mptcp/options.c b/net/mptcp/options.c
> index 370c3836b7712..1603b3702e220 100644
> --- a/net/mptcp/options.c
> +++ b/net/mptcp/options.c
> @@ -461,7 +461,7 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
>  		return false;
>  
>  	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
> -	if (subflow->fully_established || snd_data_fin_enable ||
> +	if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||

[Severity: Low]
Does this trigger a compiler error? Since the struct modification was missed
and fully_established remains a bit-field, applying READ_ONCE() here attempts
to take the address of a bit-field, which is syntactically invalid in C.

[ ... ]

> diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
> index 568a72702b080..e9dba0708ee70 100644
> --- a/net/mptcp/protocol.h
> +++ b/net/mptcp/protocol.h
> @@ -532,7 +532,7 @@ 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 : 8;
> +		__unused : 9;

[Severity: Low]
Does this increase the total bit-field group to 33 bits, causing a boundary
overflow? 

Since fully_established wasn't actually removed from the bit-field group in
this backport, incrementing the unused bits to 9 pushes the total beyond a
32-bit word size.

>  	bool	data_avail;
>  	bool	scheduled;
>  	bool	pm_listener;	    /* a listener managed by the kernel PM? */

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/2026092037-islamic-default-0aca@gregkh?part=1

Re: Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

[Matthieu Baerts]

Hello,

On 20/09/2026 09:48, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] mptcp: build failure due to READ_ONCE() on bit-field

Mmh, I missed the fact this commit has already been backported in commit
477aa7116a76 ("mptcp: annotate data-races around subflow
->fully_established"), but mostly reverted by caa4a79f74f3 ("mptcp:
remove unneeded READ_ONCE() annotation").

I don't know what's better here: either we leave it like that, and I can
fix the size of the bit-field. Or we drop patch 1 and 2, and I resolve
the small conflict on patch 3/5: commit 2b0f561f21b2 ("mptcp: avoid
unneeded actions on subflow reset"). I can send a v2, and we can drop it
if the other solution has been preferred.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

[Greg KH]

On Sun, Sep 20, 2026 at 11:33:47AM +0200, Matthieu Baerts wrote:
> Hello,
> 
> On 20/09/2026 09:48, sashiko-bot@kernel.org wrote:
> > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > - [Low] mptcp: build failure due to READ_ONCE() on bit-field
> 
> Mmh, I missed the fact this commit has already been backported in commit
> 477aa7116a76 ("mptcp: annotate data-races around subflow
> ->fully_established"), but mostly reverted by caa4a79f74f3 ("mptcp:
> remove unneeded READ_ONCE() annotation").
> 
> I don't know what's better here: either we leave it like that, and I can
> fix the size of the bit-field. Or we drop patch 1 and 2, and I resolve
> the small conflict on patch 3/5: commit 2b0f561f21b2 ("mptcp: avoid
> unneeded actions on subflow reset"). I can send a v2, and we can drop it
> if the other solution has been preferred.

Your v2 looks good, thanks for that, I'll go replace the patches with
those.

greg k-h

Re: Patch "mptcp: annotate data-races around subflow->fully_established" has been added to the 6.12-stable tree

[Matthieu Baerts]

On 20/09/2026 15:10, Greg KH wrote:
> On Sun, Sep 20, 2026 at 11:33:47AM +0200, Matthieu Baerts wrote:
>> Hello,
>>
>> On 20/09/2026 09:48, sashiko-bot@kernel.org wrote:
>>> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
>>> - [Low] mptcp: build failure due to READ_ONCE() on bit-field
>>
>> Mmh, I missed the fact this commit has already been backported in commit
>> 477aa7116a76 ("mptcp: annotate data-races around subflow
>> ->fully_established"), but mostly reverted by caa4a79f74f3 ("mptcp:
>> remove unneeded READ_ONCE() annotation").
>>
>> I don't know what's better here: either we leave it like that, and I can
>> fix the size of the bit-field. Or we drop patch 1 and 2, and I resolve
>> the small conflict on patch 3/5: commit 2b0f561f21b2 ("mptcp: avoid
>> unneeded actions on subflow reset"). I can send a v2, and we can drop it
>> if the other solution has been preferred.
> 
> Your v2 looks good, thanks for that, I'll go replace the patches with
> those.

Thank you! And sorry for the extra work :)

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

[PATCH 6.12.y 2/5] mptcp: remove unneeded READ_ONCE() annotation

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

commit caa4a79f74f32084ce28aee8653bc04df745970d upstream.

The subflow->fully_established flag is always written under the subflow
socket lock. Reading such value under the same lock does not require any
ONCE annotation.

Fixes: 581c8cbfa934 ("mptcp: annotate data-races around subflow->fully_established")
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>
Link: https://patch.msgid.link/20260908-net-mptcp-misc-fixes-7-3-rc1-v2-10-df1de70348b6@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 2b0f561f21b2 ("mptcp: avoid unneeded actions on subflow reset")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/options.c  | 4 ++--
 net/mptcp/protocol.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 123c3691833f..d238dd374ce9 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -532,7 +532,7 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 		return false;
 
 	/* MPC/MPJ needed only on 3rd ack packet, DATA_FIN and TCP shutdown take precedence */
-	if (READ_ONCE(subflow->fully_established) || snd_data_fin_enable ||
+	if (subflow->fully_established || snd_data_fin_enable ||
 	    subflow->snd_isn != TCP_SKB_CB(skb)->seq ||
 	    sk->sk_state != TCP_ESTABLISHED)
 		return false;
@@ -999,7 +999,7 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 	/* here we can process OoO, in-window pkts, only in-sequence 4th ack
 	 * will make the subflow fully established
 	 */
-	if (likely(READ_ONCE(subflow->fully_established))) {
+	if (likely(subflow->fully_established)) {
 		/* on passive sockets, check for 3rd ack retransmission
 		 * note that msk is always set by subflow_syn_recv_sock()
 		 * for mp_join subflows
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a4054ed24605..2f34e92d9cce 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3685,7 +3685,7 @@ static void schedule_3rdack_retransmission(struct sock *ssk)
 	struct tcp_sock *tp = tcp_sk(ssk);
 	unsigned long timeout;
 
-	if (READ_ONCE(mptcp_subflow_ctx(ssk)->fully_established))
+	if (mptcp_subflow_ctx(ssk)->fully_established)
 		return;
 
 	/* reschedule with a timeout above RTT, as we must look only for drop */
-- 
2.55.0

[PATCH 6.12.y 3/5] mptcp: avoid unneeded actions on subflow reset

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

commit 2b0f561f21b27c40c91ea4975268a06092bd7e9c upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-1-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Note: conflict in protocol.c, because commit e0ca4057e0ec ("mptcp:
  micro-optimize __mptcp_move_skb()") is not in this version, and is
  part of a consequent rx path refactor. The conflict is in the context,
  and is easy to resolve, "done = true" can be moved along without
  consequences. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c |  6 +++---
 net/mptcp/protocol.h |  3 ++-
 net/mptcp/subflow.c  | 11 +++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2f34e92d9cce..ff63ba5ee464 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -747,13 +747,13 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
 				mptcp_dss_corruption(msk, ssk);
 			}
 		} else {
+			sk_eat_skb(ssk, skb);
+			done = true;
+
 			if (unlikely(!fin)) {
 				DEBUG_NET_WARN_ON_ONCE(1);
 				mptcp_dss_corruption(msk, ssk);
 			}
-
-			sk_eat_skb(ssk, skb);
-			done = true;
 		}
 
 		WRITE_ONCE(tp->copied_seq, seq);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index cd4481c93b6d..436d3c92ec4a 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -545,7 +545,8 @@ 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 267e0424eea5..cfa029b4d7f3 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -440,6 +440,10 @@ 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))
@@ -1857,6 +1861,13 @@ 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 "mptcp: avoid unneeded actions on subflow reset" has been added to the 6.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    mptcp: avoid unneeded actions on subflow reset

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-avoid-unneeded-actions-on-subflow-reset.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-338600-greg=kroah.com@vger.kernel.org Sat Sep 19 21:57:17 2026
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 19 Sep 2026 21:56:46 +0200
Subject: mptcp: avoid unneeded actions on subflow reset
To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: Paolo Abeni <pabeni@redhat.com>, sashal@kernel.org, Xinyang Ge <xinyang@anthropic.com>, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20260919195642.1977885-10-matttbe@kernel.org>

From: Paolo Abeni <pabeni@redhat.com>

commit 2b0f561f21b27c40c91ea4975268a06092bd7e9c upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-1-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Note: conflict in protocol.c, because commit e0ca4057e0ec ("mptcp:
  micro-optimize __mptcp_move_skb()") is not in this version, and is
  part of a consequent rx path refactor. The conflict is in the context,
  and is easy to resolve, "done = true" can be moved along without
  consequences. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/protocol.c |    6 +++---
 net/mptcp/protocol.h |    3 ++-
 net/mptcp/subflow.c  |   11 +++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -747,13 +747,13 @@ static bool __mptcp_move_skbs_from_subfl
 				mptcp_dss_corruption(msk, ssk);
 			}
 		} else {
+			sk_eat_skb(ssk, skb);
+			done = true;
+
 			if (unlikely(!fin)) {
 				DEBUG_NET_WARN_ON_ONCE(1);
 				mptcp_dss_corruption(msk, ssk);
 			}
-
-			sk_eat_skb(ssk, skb);
-			done = true;
 		}
 
 		WRITE_ONCE(tp->copied_seq, seq);
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -545,7 +545,8 @@ 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? */
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -440,6 +440,10 @@ void mptcp_subflow_reset(struct sock *ss
 	/* 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))
@@ -1857,6 +1861,13 @@ static void subflow_state_change(struct
 
 	__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.


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-6.12/mptcp-annotate-data-races-around-subflow-fully_established.patch
queue-6.12/selftests-mptcp-fix-an-uaf-in-mptcp_connect.c.patch
queue-6.12/mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
queue-6.12/mptcp-syncookies-remember-the-request-backup-flag.patch
queue-6.12/mptcp-remove-unneeded-read_once-annotation.patch
queue-6.12/mptcp-close-race-between-scheduler-and-state-change.patch
queue-6.12/tcp-use-gfp_atomic-in-tcp_send_active_reset.patch
queue-6.12/mptcp-avoid-unneeded-actions-on-subflow-reset.patch
queue-6.12/mptcp-options-handle-mpc-data-csum-reqd-no-csum.patch
queue-6.12/mptcp-subflow-no-need-to-copy-thmac-during-ulp_clone.patch

[PATCH 6.12.y 4/5] mptcp: close race between scheduler and state change

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

commit 42064de57fb83231fcc89663a94885f228a1ee53 upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-2-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@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 ff63ba5ee464..1304f3cb6d14 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1567,7 +1567,9 @@ 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 "mptcp: close race between scheduler and state change" has been added to the 6.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    mptcp: close race between scheduler and state change

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-close-race-between-scheduler-and-state-change.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-338601-greg=kroah.com@vger.kernel.org Sat Sep 19 21:57:24 2026
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 19 Sep 2026 21:56:47 +0200
Subject: mptcp: close race between scheduler and state change
To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: Paolo Abeni <pabeni@redhat.com>, sashal@kernel.org, Shardul Bankar <shardul.b@mpiricsoftware.com>, Xinyang Ge <xinyang@anthropic.com>, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20260919195642.1977885-11-matttbe@kernel.org>

From: Paolo Abeni <pabeni@redhat.com>

commit 42064de57fb83231fcc89663a94885f228a1ee53 upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-2-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/protocol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1567,7 +1567,9 @@ struct sock *mptcp_subflow_get_send(stru
 
 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);
 }
 


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-6.12/mptcp-annotate-data-races-around-subflow-fully_established.patch
queue-6.12/selftests-mptcp-fix-an-uaf-in-mptcp_connect.c.patch
queue-6.12/mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
queue-6.12/mptcp-syncookies-remember-the-request-backup-flag.patch
queue-6.12/mptcp-remove-unneeded-read_once-annotation.patch
queue-6.12/mptcp-close-race-between-scheduler-and-state-change.patch
queue-6.12/tcp-use-gfp_atomic-in-tcp_send_active_reset.patch
queue-6.12/mptcp-avoid-unneeded-actions-on-subflow-reset.patch
queue-6.12/mptcp-options-handle-mpc-data-csum-reqd-no-csum.patch
queue-6.12/mptcp-subflow-no-need-to-copy-thmac-during-ulp_clone.patch

[PATCH 6.12.y 5/5] mptcp: fix bad accounting in __mptcp_subflow_push_pending()

[Matthieu Baerts (NGI0)]

From: Paolo Abeni <pabeni@redhat.com>

commit f3ef03357396d4b147d8e76c75fb612c2f264ffc upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-3-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@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 1304f3cb6d14..ee160c783ff5 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1757,7 +1757,8 @@ 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

Patch "mptcp: fix bad accounting in __mptcp_subflow_push_pending()" has been added to the 6.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    mptcp: fix bad accounting in __mptcp_subflow_push_pending()

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-338602-greg=kroah.com@vger.kernel.org Sat Sep 19 21:57:31 2026
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 19 Sep 2026 21:56:48 +0200
Subject: mptcp: fix bad accounting in __mptcp_subflow_push_pending()
To: mptcp@lists.linux.dev, stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: Paolo Abeni <pabeni@redhat.com>, sashal@kernel.org, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20260919195642.1977885-12-matttbe@kernel.org>

From: Paolo Abeni <pabeni@redhat.com>

commit f3ef03357396d4b147d8e76c75fb612c2f264ffc upstream.

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>
Link: https://patch.msgid.link/20260917-net-mptcp-misc-fixes-7-3-rc4-v2-3-0cf5c72667c8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/protocol.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1757,7 +1757,8 @@ static void __mptcp_subflow_push_pending
 			ret = __subflow_push_pending(sk, ssk, &info);
 			if (ret <= 0)
 				keep_pushing = false;
-			copied += ret;
+			else
+				copied += ret;
 		}
 
 		mptcp_for_each_subflow(msk, subflow) {


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-6.12/mptcp-annotate-data-races-around-subflow-fully_established.patch
queue-6.12/selftests-mptcp-fix-an-uaf-in-mptcp_connect.c.patch
queue-6.12/mptcp-fix-bad-accounting-in-__mptcp_subflow_push_pending.patch
queue-6.12/mptcp-syncookies-remember-the-request-backup-flag.patch
queue-6.12/mptcp-remove-unneeded-read_once-annotation.patch
queue-6.12/mptcp-close-race-between-scheduler-and-state-change.patch
queue-6.12/tcp-use-gfp_atomic-in-tcp_send_active_reset.patch
queue-6.12/mptcp-avoid-unneeded-actions-on-subflow-reset.patch
queue-6.12/mptcp-options-handle-mpc-data-csum-reqd-no-csum.patch
queue-6.12/mptcp-subflow-no-need-to-copy-thmac-during-ulp_clone.patch