[PATCH net 0/3] mptcp: Fixes and maintainer email update for v6.6

[PATCH net 0/3] mptcp: Fixes and maintainer email update for v6.6

[Mat Martineau]

Patch 1 addresses a race condition in MPTCP "delegated actions"
infrastructure. Affects v5.19 and later.

Patch 2 removes an unnecessary restriction that did not allow additional
outgoing subflows using the local address of the initial MPTCP subflow.
v5.16 and later.

Patch 3 updates Matthieu's email address.

Signed-off-by: Mat Martineau <martineau@kernel.org>
---
Geliang Tang (1):
      mptcp: userspace pm allow creating id 0 subflow

Matthieu Baerts (1):
      MAINTAINERS: update Matthieu's email address

Paolo Abeni (1):
      mptcp: fix delegated action races

 .mailmap                 |  1 +
 MAINTAINERS              |  2 +-
 net/mptcp/pm_userspace.c |  6 ------
 net/mptcp/protocol.c     | 28 ++++++++++++++--------------
 net/mptcp/protocol.h     | 35 ++++++++++++-----------------------
 net/mptcp/subflow.c      | 10 ++++++++--
 6 files changed, 36 insertions(+), 46 deletions(-)
---
base-commit: 0add5c597f3253a9c6108a0a81d57f44ab0d9d30
change-id: 20231004-send-net-20231004-7e1422eddf40

Best regards,
-- 
Mat Martineau <martineau@kernel.org>

[PATCH net 1/3] mptcp: fix delegated action races

[Mat Martineau]

From: Paolo Abeni <pabeni@redhat.com>

The delegated action infrastructure is prone to the following
race: different CPUs can try to schedule different delegated
actions on the same subflow at the same time.

Each of them will check different bits via mptcp_subflow_delegate(),
and will try to schedule the action on the related per-cpu napi
instance.

Depending on the timing, both can observe an empty delegated list
node, causing the same entry to be added simultaneously on two different
lists.

The root cause is that the delegated actions infra does not provide
a single synchronization point. Address the issue reserving an additional
bit to mark the subflow as scheduled for delegation. Acquiring such bit
guarantee the caller to own the delegated list node, and being able to
safely schedule the subflow.

Clear such bit only when the subflow scheduling is completed, ensuring
proper barrier in place.

Additionally swap the meaning of the delegated_action bitmask, to allow
the usage of the existing helper to set multiple bit at once.

Fixes: bcd97734318d ("mptcp: use delegate action to schedule 3rd ack retrans")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
---
 net/mptcp/protocol.c | 28 ++++++++++++++--------------
 net/mptcp/protocol.h | 35 ++++++++++++-----------------------
 net/mptcp/subflow.c  | 10 ++++++++--
 3 files changed, 34 insertions(+), 39 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index e252539b1e19..c3b83cb390d9 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3425,24 +3425,21 @@ static void schedule_3rdack_retransmission(struct sock *ssk)
 	sk_reset_timer(ssk, &icsk->icsk_delack_timer, timeout);
 }
 
-void mptcp_subflow_process_delegated(struct sock *ssk)
+void mptcp_subflow_process_delegated(struct sock *ssk, long status)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
 	struct sock *sk = subflow->conn;
 
-	if (test_bit(MPTCP_DELEGATE_SEND, &subflow->delegated_status)) {
+	if (status & BIT(MPTCP_DELEGATE_SEND)) {
 		mptcp_data_lock(sk);
 		if (!sock_owned_by_user(sk))
 			__mptcp_subflow_push_pending(sk, ssk, true);
 		else
 			__set_bit(MPTCP_PUSH_PENDING, &mptcp_sk(sk)->cb_flags);
 		mptcp_data_unlock(sk);
-		mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_SEND);
 	}
-	if (test_bit(MPTCP_DELEGATE_ACK, &subflow->delegated_status)) {
+	if (status & BIT(MPTCP_DELEGATE_ACK))
 		schedule_3rdack_retransmission(ssk);
-		mptcp_subflow_delegated_done(subflow, MPTCP_DELEGATE_ACK);
-	}
 }
 
 static int mptcp_hash(struct sock *sk)
@@ -3968,14 +3965,17 @@ static int mptcp_napi_poll(struct napi_struct *napi, int budget)
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
 		bh_lock_sock_nested(ssk);
-		if (!sock_owned_by_user(ssk) &&
-		    mptcp_subflow_has_delegated_action(subflow))
-			mptcp_subflow_process_delegated(ssk);
-		/* ... elsewhere tcp_release_cb_override already processed
-		 * the action or will do at next release_sock().
-		 * In both case must dequeue the subflow here - on the same
-		 * CPU that scheduled it.
-		 */
+		if (!sock_owned_by_user(ssk)) {
+			mptcp_subflow_process_delegated(ssk, xchg(&subflow->delegated_status, 0));
+		} else {
+			/* tcp_release_cb_override already processed
+			 * the action or will do at next release_sock().
+			 * In both case must dequeue the subflow here - on the same
+			 * CPU that scheduled it.
+			 */
+			smp_wmb();
+			clear_bit(MPTCP_DELEGATE_SCHEDULED, &subflow->delegated_status);
+		}
 		bh_unlock_sock(ssk);
 		sock_put(ssk);
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index ed61d6850cce..3612545fa62e 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -444,9 +444,11 @@ struct mptcp_delegated_action {
 
 DECLARE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
 
-#define MPTCP_DELEGATE_SEND		0
-#define MPTCP_DELEGATE_ACK		1
+#define MPTCP_DELEGATE_SCHEDULED	0
+#define MPTCP_DELEGATE_SEND		1
+#define MPTCP_DELEGATE_ACK		2
 
+#define MPTCP_DELEGATE_ACTIONS_MASK	(~BIT(MPTCP_DELEGATE_SCHEDULED))
 /* MPTCP subflow context */
 struct mptcp_subflow_context {
 	struct	list_head node;/* conn_list of subflows */
@@ -564,23 +566,24 @@ mptcp_subflow_get_mapped_dsn(const struct mptcp_subflow_context *subflow)
 	return subflow->map_seq + mptcp_subflow_get_map_offset(subflow);
 }
 
-void mptcp_subflow_process_delegated(struct sock *ssk);
+void mptcp_subflow_process_delegated(struct sock *ssk, long actions);
 
 static inline void mptcp_subflow_delegate(struct mptcp_subflow_context *subflow, int action)
 {
+	long old, set_bits = BIT(MPTCP_DELEGATE_SCHEDULED) | BIT(action);
 	struct mptcp_delegated_action *delegated;
 	bool schedule;
 
 	/* the caller held the subflow bh socket lock */
 	lockdep_assert_in_softirq();
 
-	/* The implied barrier pairs with mptcp_subflow_delegated_done(), and
-	 * ensures the below list check sees list updates done prior to status
-	 * bit changes
+	/* The implied barrier pairs with tcp_release_cb_override()
+	 * mptcp_napi_poll(), and ensures the below list check sees list
+	 * updates done prior to delegated status bits changes
 	 */
-	if (!test_and_set_bit(action, &subflow->delegated_status)) {
-		/* still on delegated list from previous scheduling */
-		if (!list_empty(&subflow->delegated_node))
+	old = set_mask_bits(&subflow->delegated_status, 0, set_bits);
+	if (!(old & BIT(MPTCP_DELEGATE_SCHEDULED))) {
+		if (WARN_ON_ONCE(!list_empty(&subflow->delegated_node)))
 			return;
 
 		delegated = this_cpu_ptr(&mptcp_delegated_actions);
@@ -605,20 +608,6 @@ mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
 	return ret;
 }
 
-static inline bool mptcp_subflow_has_delegated_action(const struct mptcp_subflow_context *subflow)
-{
-	return !!READ_ONCE(subflow->delegated_status);
-}
-
-static inline void mptcp_subflow_delegated_done(struct mptcp_subflow_context *subflow, int action)
-{
-	/* pairs with mptcp_subflow_delegate, ensures delegate_node is updated before
-	 * touching the status bit
-	 */
-	smp_wmb();
-	clear_bit(action, &subflow->delegated_status);
-}
-
 int mptcp_is_enabled(const struct net *net);
 unsigned int mptcp_get_add_addr_timeout(const struct net *net);
 int mptcp_is_checksum_enabled(const struct net *net);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 918c1a235790..9c1f8d1d63d2 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1956,9 +1956,15 @@ static void subflow_ulp_clone(const struct request_sock *req,
 static void tcp_release_cb_override(struct sock *ssk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
+	long status;
 
-	if (mptcp_subflow_has_delegated_action(subflow))
-		mptcp_subflow_process_delegated(ssk);
+	/* process and clear all the pending actions, but leave the subflow into
+	 * the napi queue. To respect locking, only the same CPU that originated
+	 * the action can touch the list. mptcp_napi_poll will take care of it.
+	 */
+	status = set_mask_bits(&subflow->delegated_status, MPTCP_DELEGATE_ACTIONS_MASK, 0);
+	if (status)
+		mptcp_subflow_process_delegated(ssk, status);
 
 	tcp_release_cb(ssk);
 }

-- 
2.41.0

[PATCH net 2/3] mptcp: userspace pm allow creating id 0 subflow

[Mat Martineau]

From: Geliang Tang <geliang.tang@suse.com>

This patch drops id 0 limitation in mptcp_nl_cmd_sf_create() to allow
creating additional subflows with the local addr ID 0.

There is no reason not to allow additional subflows from this local
address: we should be able to create new subflows from the initial
endpoint. This limitation was breaking fullmesh support from userspace.

Fixes: 702c2f646d42 ("mptcp: netlink: allow userspace-driven subflow establishment")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/391
Cc: stable@vger.kernel.org
Suggested-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
---
 net/mptcp/pm_userspace.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index b5a8aa4c1ebd..d042d32beb4d 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -307,12 +307,6 @@ int mptcp_nl_cmd_sf_create(struct sk_buff *skb, struct genl_info *info)
 		goto create_err;
 	}
 
-	if (addr_l.id == 0) {
-		NL_SET_ERR_MSG_ATTR(info->extack, laddr, "missing local addr id");
-		err = -EINVAL;
-		goto create_err;
-	}
-
 	err = mptcp_pm_parse_addr(raddr, info, &addr_r);
 	if (err < 0) {
 		NL_SET_ERR_MSG_ATTR(info->extack, raddr, "error parsing remote addr");

-- 
2.41.0

[PATCH net 3/3] MAINTAINERS: update Matthieu's email address

[Mat Martineau]

From: Matthieu Baerts <matttbe@kernel.org>

Use my kernel.org account instead.

The other one will bounce by the end of the year.

Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
---
 .mailmap    | 1 +
 MAINTAINERS | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/.mailmap b/.mailmap
index a0a6efe87186..c80903efec75 100644
--- a/.mailmap
+++ b/.mailmap
@@ -377,6 +377,7 @@ Matthew Wilcox <willy@infradead.org> <willy@debian.org>
 Matthew Wilcox <willy@infradead.org> <willy@linux.intel.com>
 Matthew Wilcox <willy@infradead.org> <willy@parisc-linux.org>
 Matthias Fuchs <socketcan@esd.eu> <matthias.fuchs@esd.eu>
+Matthieu Baerts <matttbe@kernel.org> <matthieu.baerts@tessares.net>
 Matthieu CASTET <castet.matthieu@free.fr>
 Matti Vaittinen <mazziesaccount@gmail.com> <matti.vaittinen@fi.rohmeurope.com>
 Matt Ranostay <matt.ranostay@konsulko.com> <matt@ranostay.consulting>
diff --git a/MAINTAINERS b/MAINTAINERS
index 9275708c9b96..0bb5451e9b86 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14942,7 +14942,7 @@ K:	macsec
 K:	\bmdo_
 
 NETWORKING [MPTCP]
-M:	Matthieu Baerts <matthieu.baerts@tessares.net>
+M:	Matthieu Baerts <matttbe@kernel.org>
 M:	Mat Martineau <martineau@kernel.org>
 L:	netdev@vger.kernel.org
 L:	mptcp@lists.linux.dev

-- 
2.41.0

Re: [PATCH net 0/3] mptcp: Fixes and maintainer email update for v6.6

[patchwork-bot+netdevbpf]

Hello:

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

On Wed, 04 Oct 2023 13:38:10 -0700 you wrote:
> Patch 1 addresses a race condition in MPTCP "delegated actions"
> infrastructure. Affects v5.19 and later.
> 
> Patch 2 removes an unnecessary restriction that did not allow additional
> outgoing subflows using the local address of the initial MPTCP subflow.
> v5.16 and later.
> 
> [...]

Here is the summary with links:
  - [net,1/3] mptcp: fix delegated action races
    https://git.kernel.org/netdev/net/c/a5efdbcece83
  - [net,2/3] mptcp: userspace pm allow creating id 0 subflow
    https://git.kernel.org/netdev/net/c/e5ed101a6028
  - [net,3/3] MAINTAINERS: update Matthieu's email address
    https://git.kernel.org/netdev/net/c/8eed6ee362b0

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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