[PATCH net 0/6] mptcp: Connection and accounting fixes

[PATCH net 0/6] mptcp: Connection and accounting fixes

[Mat Martineau]

Here are some miscellaneous fixes for MPTCP:

Patch 1 modifies an MPTCP hash so it doesn't depend on one of skb->dev
and skb->sk being non-NULL.

Patch 2 removes an extra destructor call when rejecting a join due to
port mismatch.

Patches 3 and 5 more cleanly handle error conditions with MP_JOIN and
syncookies, and update a related self test.

Patch 4 makes sure packets that trigger a subflow TCP reset during MPTCP
option header processing are correctly dropped.

Patch 6 addresses a rmem accounting issue that could keep packets in
subflow receive buffers longer than necessary, delaying MPTCP-level
ACKs.


Jianguo Wu (5):
  mptcp: fix warning in __skb_flow_dissect() when do syn cookie for
    subflow join
  mptcp: remove redundant req destruct in subflow_check_req()
  mptcp: fix syncookie process if mptcp can not_accept new subflow
  mptcp: avoid processing packet if a subflow reset
  selftests: mptcp: fix case multiple subflows limited by server

Paolo Abeni (1):
  mptcp: properly account bulk freed memory

 include/net/mptcp.h                           |  5 +++--
 net/ipv4/tcp_input.c                          | 19 +++++++++++++++----
 net/mptcp/mib.c                               |  1 +
 net/mptcp/mib.h                               |  1 +
 net/mptcp/options.c                           | 19 +++++++++++++------
 net/mptcp/protocol.c                          | 12 +++++++-----
 net/mptcp/protocol.h                          | 10 +++++++++-
 net/mptcp/subflow.c                           | 11 +++--------
 net/mptcp/syncookies.c                        | 16 +++++++++++++++-
 .../testing/selftests/net/mptcp/mptcp_join.sh |  2 +-
 10 files changed, 68 insertions(+), 28 deletions(-)

-- 
2.32.0

[PATCH net 1/6] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join

[Mat Martineau]

From: Jianguo Wu <wujianguo@chinatelecom.cn>

I did stress test with wrk[1] and webfsd[2] with the assistance of
mptcp-tools[3]:

  Server side:
      ./use_mptcp.sh webfsd -4 -R /tmp/ -p 8099
  Client side:
      ./use_mptcp.sh wrk -c 200 -d 30 -t 4 http://192.168.174.129:8099/

and got the following warning message:

[   55.552626] TCP: request_sock_subflow: Possible SYN flooding on port 8099. Sending cookies.  Check SNMP counters.
[   55.553024] ------------[ cut here ]------------
[   55.553027] WARNING: CPU: 0 PID: 10 at net/core/flow_dissector.c:984 __skb_flow_dissect+0x280/0x1650
...
[   55.553117] CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.12.0+ #18
[   55.553121] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
[   55.553124] RIP: 0010:__skb_flow_dissect+0x280/0x1650
...
[   55.553133] RSP: 0018:ffffb79580087770 EFLAGS: 00010246
[   55.553137] RAX: 0000000000000000 RBX: ffffffff8ddb58e0 RCX: ffffb79580087888
[   55.553139] RDX: ffffffff8ddb58e0 RSI: ffff8f7e4652b600 RDI: 0000000000000000
[   55.553141] RBP: ffffb79580087858 R08: 0000000000000000 R09: 0000000000000008
[   55.553143] R10: 000000008c622965 R11: 00000000d3313a5b R12: ffff8f7e4652b600
[   55.553146] R13: ffff8f7e465c9062 R14: 0000000000000000 R15: ffffb79580087888
[   55.553149] FS:  0000000000000000(0000) GS:ffff8f7f75e00000(0000) knlGS:0000000000000000
[   55.553152] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   55.553154] CR2: 00007f73d1d19000 CR3: 0000000135e10004 CR4: 00000000003706f0
[   55.553160] Call Trace:
[   55.553166]  ? __sha256_final+0x67/0xd0
[   55.553173]  ? sha256+0x7e/0xa0
[   55.553177]  __skb_get_hash+0x57/0x210
[   55.553182]  subflow_init_req_cookie_join_save+0xac/0xc0
[   55.553189]  subflow_check_req+0x474/0x550
[   55.553195]  ? ip_route_output_key_hash+0x67/0x90
[   55.553200]  ? xfrm_lookup_route+0x1d/0xa0
[   55.553207]  subflow_v4_route_req+0x8e/0xd0
[   55.553212]  tcp_conn_request+0x31e/0xab0
[   55.553218]  ? selinux_socket_sock_rcv_skb+0x116/0x210
[   55.553224]  ? tcp_rcv_state_process+0x179/0x6d0
[   55.553229]  tcp_rcv_state_process+0x179/0x6d0
[   55.553235]  tcp_v4_do_rcv+0xaf/0x220
[   55.553239]  tcp_v4_rcv+0xce4/0xd80
[   55.553243]  ? ip_route_input_rcu+0x246/0x260
[   55.553248]  ip_protocol_deliver_rcu+0x35/0x1b0
[   55.553253]  ip_local_deliver_finish+0x44/0x50
[   55.553258]  ip_local_deliver+0x6c/0x110
[   55.553262]  ? ip_rcv_finish_core.isra.19+0x5a/0x400
[   55.553267]  ip_rcv+0xd1/0xe0
...

After debugging, I found in __skb_flow_dissect(), skb->dev and skb->sk
are both NULL, then net is NULL, and trigger WARN_ON_ONCE(!net),
actually net is always NULL in this code path, as skb->dev is set to
NULL in tcp_v4_rcv(), and skb->sk is never set.

Code snippet in __skb_flow_dissect() that trigger warning:
  975         if (skb) {
  976                 if (!net) {
  977                         if (skb->dev)
  978                                 net = dev_net(skb->dev);
  979                         else if (skb->sk)
  980                                 net = sock_net(skb->sk);
  981                 }
  982         }
  983
  984         WARN_ON_ONCE(!net);

So, using seq and transport header derived hash.

[1] https://github.com/wg/wrk
[2] https://github.com/ourway/webfsd
[3] https://github.com/pabeni/mptcp-tools

Fixes: 9466a1ccebbe ("mptcp: enable JOIN requests even if cookies are in use")
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Suggested-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/syncookies.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c
index abe0fd099746..37127781aee9 100644
--- a/net/mptcp/syncookies.c
+++ b/net/mptcp/syncookies.c
@@ -37,7 +37,21 @@ static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp
 
 static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net)
 {
-	u32 i = skb_get_hash(skb) ^ net_hash_mix(net);
+	static u32 mptcp_join_hash_secret __read_mostly;
+	struct tcphdr *th = tcp_hdr(skb);
+	u32 seq, i;
+
+	net_get_random_once(&mptcp_join_hash_secret,
+			    sizeof(mptcp_join_hash_secret));
+
+	if (th->syn)
+		seq = TCP_SKB_CB(skb)->seq;
+	else
+		seq = TCP_SKB_CB(skb)->seq - 1;
+
+	i = jhash_3words(seq, net_hash_mix(net),
+			 (__force __u32)th->source << 16 | (__force __u32)th->dest,
+			 mptcp_join_hash_secret);
 
 	return i % ARRAY_SIZE(join_entries);
 }
-- 
2.32.0

[PATCH net 2/6] mptcp: remove redundant req destruct in subflow_check_req()

[Mat Martineau]

From: Jianguo Wu <wujianguo@chinatelecom.cn>

In subflow_check_req(), if subflow sport is mismatch, will put msk,
destroy token, and destruct req, then return -EPERM, which can be
done by subflow_req_destructor() via:

  tcp_conn_request()
    |--__reqsk_free()
      |--subflow_req_destructor()

So we should remove these redundant code, otherwise will call
tcp_v4_reqsk_destructor() twice, and may double free
inet_rsk(req)->ireq_opt.

Fixes: 5bc56388c74f ("mptcp: add port number check for MP_JOIN")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/subflow.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 66d0b1893d26..b15e2017168d 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -214,11 +214,6 @@ static int subflow_check_req(struct request_sock *req,
 				 ntohs(inet_sk(sk_listener)->inet_sport),
 				 ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
 			if (!mptcp_pm_sport_in_anno_list(subflow_req->msk, sk_listener)) {
-				sock_put((struct sock *)subflow_req->msk);
-				mptcp_token_destroy_request(req);
-				tcp_request_sock_ops.destructor(req);
-				subflow_req->msk = NULL;
-				subflow_req->mp_join = 0;
 				SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
 				return -EPERM;
 			}
-- 
2.32.0

[PATCH net 3/6] mptcp: fix syncookie process if mptcp can not_accept new subflow

[Mat Martineau]

From: Jianguo Wu <wujianguo@chinatelecom.cn>

Lots of "TCP: tcp_fin: Impossible, sk->sk_state=7" in client side
when doing stress testing using wrk and webfsd.

There are at least two cases may trigger this warning:
1.mptcp is in syncookie, and server recv MP_JOIN SYN request,
  in subflow_check_req(), the mptcp_can_accept_new_subflow()
  return false, so subflow_init_req_cookie_join_save() isn't
  called, i.e. not store the data present in the MP_JOIN syn
  request and the random nonce in hash table - join_entries[],
  but still send synack. When recv 3rd-ack,
  mptcp_token_join_cookie_init_state() will return false, and
  3rd-ack is dropped, then if mptcp conn is closed by client,
  client will send a DATA_FIN and a MPTCP FIN, the DATA_FIN
  doesn't have MP_CAPABLE or MP_JOIN,
  so mptcp_subflow_init_cookie_req() will return 0, and pass
  the cookie check, MP_JOIN request is fallback to normal TCP.
  Server will send a TCP FIN if closed, in client side,
  when process TCP FIN, it will do reset, the code path is:
    tcp_data_queue()->mptcp_incoming_options()
      ->check_fully_established()->mptcp_subflow_reset().
  mptcp_subflow_reset() will set sock state to TCP_CLOSE,
  so tcp_fin will hit TCP_CLOSE, and print the warning.

2.mptcp is in syncookie, and server recv 3rd-ack, in
  mptcp_subflow_init_cookie_req(), mptcp_can_accept_new_subflow()
  return false, and subflow_req->mp_join is not set to 1,
  so in subflow_syn_recv_sock() will not reset the MP_JOIN
  subflow, but fallback to normal TCP, and then the same thing
  happens when server will send a TCP FIN if closed.

For case1, subflow_check_req() return -EPERM,
then tcp_conn_request() will drop MP_JOIN SYN.

For case2, let subflow_syn_recv_sock() call
mptcp_can_accept_new_subflow(), and do fatal fallback, send reset.

Fixes: 9466a1ccebbe ("mptcp: enable JOIN requests even if cookies are in use")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/subflow.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index b15e2017168d..966f777d35ce 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -225,6 +225,8 @@ static int subflow_check_req(struct request_sock *req,
 		if (unlikely(req->syncookie)) {
 			if (mptcp_can_accept_new_subflow(subflow_req->msk))
 				subflow_init_req_cookie_join_save(subflow_req, skb);
+			else
+				return -EPERM;
 		}
 
 		pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
@@ -264,9 +266,7 @@ int mptcp_subflow_init_cookie_req(struct request_sock *req,
 		if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
 			return -EINVAL;
 
-		if (mptcp_can_accept_new_subflow(subflow_req->msk))
-			subflow_req->mp_join = 1;
-
+		subflow_req->mp_join = 1;
 		subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
 	}
 
-- 
2.32.0

[PATCH net 4/6] mptcp: avoid processing packet if a subflow reset

[Mat Martineau]

From: Jianguo Wu <wujianguo@chinatelecom.cn>

If check_fully_established() causes a subflow reset, it should not
continue to process the packet in tcp_data_queue().
Add a return value to mptcp_incoming_options(), and return false if a
subflow has been reset, else return true. Then drop the packet in
tcp_data_queue()/tcp_rcv_state_process() if mptcp_incoming_options()
return false.

Fixes: d582484726c4 ("mptcp: fix fallback for MP_JOIN subflows")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 include/net/mptcp.h  |  5 +++--
 net/ipv4/tcp_input.c | 19 +++++++++++++++----
 net/mptcp/options.c  | 19 +++++++++++++------
 3 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index cb580b06152f..8b5af683a818 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -105,7 +105,7 @@ bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
 bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
 			       unsigned int *size, unsigned int remaining,
 			       struct mptcp_out_options *opts);
-void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb);
+bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb);
 
 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
 			 struct mptcp_out_options *opts);
@@ -227,9 +227,10 @@ static inline bool mptcp_established_options(struct sock *sk,
 	return false;
 }
 
-static inline void mptcp_incoming_options(struct sock *sk,
+static inline bool mptcp_incoming_options(struct sock *sk,
 					  struct sk_buff *skb)
 {
+	return true;
 }
 
 static inline void mptcp_skb_ext_move(struct sk_buff *to,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a5a8d0a378b2..149ceb5c94ff 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4247,6 +4247,9 @@ void tcp_reset(struct sock *sk, struct sk_buff *skb)
 {
 	trace_tcp_receive_reset(sk);
 
+	/* mptcp can't tell us to ignore reset pkts,
+	 * so just ignore the return value of mptcp_incoming_options().
+	 */
 	if (sk_is_mptcp(sk))
 		mptcp_incoming_options(sk, skb);
 
@@ -4941,8 +4944,13 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 	bool fragstolen;
 	int eaten;
 
-	if (sk_is_mptcp(sk))
-		mptcp_incoming_options(sk, skb);
+	/* If a subflow has been reset, the packet should not continue
+	 * to be processed, drop the packet.
+	 */
+	if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb)) {
+		__kfree_skb(skb);
+		return;
+	}
 
 	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
 		__kfree_skb(skb);
@@ -6523,8 +6531,11 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 	case TCP_CLOSING:
 	case TCP_LAST_ACK:
 		if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
-			if (sk_is_mptcp(sk))
-				mptcp_incoming_options(sk, skb);
+			/* If a subflow has been reset, the packet should not
+			 * continue to be processed, drop the packet.
+			 */
+			if (sk_is_mptcp(sk) && !mptcp_incoming_options(sk, skb))
+				goto discard;
 			break;
 		}
 		fallthrough;
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index b5850afea343..4452455aef7f 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -1035,7 +1035,8 @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk,
 	return hmac == mp_opt->ahmac;
 }
 
-void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
+/* Return false if a subflow has been reset, else return true */
+bool mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
@@ -1053,12 +1054,16 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 			__mptcp_check_push(subflow->conn, sk);
 		__mptcp_data_acked(subflow->conn);
 		mptcp_data_unlock(subflow->conn);
-		return;
+		return true;
 	}
 
 	mptcp_get_options(sk, skb, &mp_opt);
+
+	/* The subflow can be in close state only if check_fully_established()
+	 * just sent a reset. If so, tell the caller to ignore the current packet.
+	 */
 	if (!check_fully_established(msk, sk, subflow, skb, &mp_opt))
-		return;
+		return sk->sk_state != TCP_CLOSE;
 
 	if (mp_opt.fastclose &&
 	    msk->local_key == mp_opt.rcvr_key) {
@@ -1100,7 +1105,7 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 	}
 
 	if (!mp_opt.dss)
-		return;
+		return true;
 
 	/* we can't wait for recvmsg() to update the ack_seq, otherwise
 	 * monodirectional flows will stuck
@@ -1119,12 +1124,12 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		    schedule_work(&msk->work))
 			sock_hold(subflow->conn);
 
-		return;
+		return true;
 	}
 
 	mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
 	if (!mpext)
-		return;
+		return true;
 
 	memset(mpext, 0, sizeof(*mpext));
 
@@ -1153,6 +1158,8 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb)
 		if (mpext->csum_reqd)
 			mpext->csum = mp_opt.csum;
 	}
+
+	return true;
 }
 
 static void mptcp_set_rwin(const struct tcp_sock *tp)
-- 
2.32.0

[PATCH net 5/6] selftests: mptcp: fix case multiple subflows limited by server

[Mat Martineau]

From: Jianguo Wu <wujianguo@chinatelecom.cn>

After patch "mptcp: fix syncookie process if mptcp can not_accept new
subflow", if subflow is limited, MP_JOIN SYN is dropped, and no SYN/ACK
will be replied.

So in case "multiple subflows limited by server", the expected SYN/ACK
number should be 1.

Fixes: 00587187ad30 ("selftests: mptcp: add test cases for mptcp join tests with syn cookies")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 tools/testing/selftests/net/mptcp/mptcp_join.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 9a191c1a5de8..f02f4de2f3a0 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1409,7 +1409,7 @@ syncookies_tests()
 	ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags subflow
 	ip netns exec $ns2 ./pm_nl_ctl add 10.0.2.2 flags subflow
 	run_tests $ns1 $ns2 10.0.1.1
-	chk_join_nr "subflows limited by server w cookies" 2 2 1
+	chk_join_nr "subflows limited by server w cookies" 2 1 1
 
 	# test signal address with cookies
 	reset_with_cookies
-- 
2.32.0

[PATCH net 6/6] mptcp: properly account bulk freed memory

[Mat Martineau]

From: Paolo Abeni <pabeni@redhat.com>

After commit 879526030c8b ("mptcp: protect the rx path with
the msk socket spinlock") the rmem currently used by a given
msk is really sk_rmem_alloc - rmem_released.

The safety check in mptcp_data_ready() does not take the above
in due account, as a result legit incoming data is kept in
subflow receive queue with no reason, delaying or blocking
MPTCP-level ack generation.

This change addresses the issue introducing a new helper to fetch
the rmem memory and using it as needed. Additionally add a MIB
counter for the exceptional event described above - the peer is
misbehaving.

Finally, introduce the required annotation when rmem_released is
updated.

Fixes: 879526030c8b ("mptcp: protect the rx path with the msk socket spinlock")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/211
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 net/mptcp/mib.c      |  1 +
 net/mptcp/mib.h      |  1 +
 net/mptcp/protocol.c | 12 +++++++-----
 net/mptcp/protocol.h | 10 +++++++++-
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
index 52ea2517e856..ff2cc0e3273d 100644
--- a/net/mptcp/mib.c
+++ b/net/mptcp/mib.c
@@ -44,6 +44,7 @@ static const struct snmp_mib mptcp_snmp_list[] = {
 	SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW),
 	SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX),
 	SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX),
+	SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 193466c9b549..0663cb12b448 100644
--- a/net/mptcp/mib.h
+++ b/net/mptcp/mib.h
@@ -37,6 +37,7 @@ enum linux_mptcp_mib_field {
 	MPTCP_MIB_RMSUBFLOW,		/* Remove a subflow */
 	MPTCP_MIB_MPPRIOTX,		/* Transmit a MP_PRIO */
 	MPTCP_MIB_MPPRIORX,		/* Received a MP_PRIO */
+	MPTCP_MIB_RCVPRUNED,		/* Incoming packet dropped due to memory limit */
 	__MPTCP_MIB_MAX
 };
 
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 7a5afa8c6866..a88924947815 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -474,7 +474,7 @@ static void mptcp_cleanup_rbuf(struct mptcp_sock *msk)
 	bool cleanup, rx_empty;
 
 	cleanup = (space > 0) && (space >= (old_space << 1));
-	rx_empty = !atomic_read(&sk->sk_rmem_alloc);
+	rx_empty = !__mptcp_rmem(sk);
 
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
@@ -720,8 +720,10 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
 		sk_rbuf = ssk_rbuf;
 
 	/* over limit? can't append more skbs to msk, Also, no need to wake-up*/
-	if (atomic_read(&sk->sk_rmem_alloc) > sk_rbuf)
+	if (__mptcp_rmem(sk) > sk_rbuf) {
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVPRUNED);
 		return;
+	}
 
 	/* Wake-up the reader only for in-sequence data */
 	mptcp_data_lock(sk);
@@ -1754,7 +1756,7 @@ static int __mptcp_recvmsg_mskq(struct mptcp_sock *msk,
 		if (!(flags & MSG_PEEK)) {
 			/* we will bulk release the skb memory later */
 			skb->destructor = NULL;
-			msk->rmem_released += skb->truesize;
+			WRITE_ONCE(msk->rmem_released, msk->rmem_released + skb->truesize);
 			__skb_unlink(skb, &msk->receive_queue);
 			__kfree_skb(skb);
 		}
@@ -1873,7 +1875,7 @@ static void __mptcp_update_rmem(struct sock *sk)
 
 	atomic_sub(msk->rmem_released, &sk->sk_rmem_alloc);
 	sk_mem_uncharge(sk, msk->rmem_released);
-	msk->rmem_released = 0;
+	WRITE_ONCE(msk->rmem_released, 0);
 }
 
 static void __mptcp_splice_receive_queue(struct sock *sk)
@@ -2380,7 +2382,7 @@ static int __mptcp_init_sock(struct sock *sk)
 	msk->out_of_order_queue = RB_ROOT;
 	msk->first_pending = NULL;
 	msk->wmem_reserved = 0;
-	msk->rmem_released = 0;
+	WRITE_ONCE(msk->rmem_released, 0);
 	msk->tx_pending_data = 0;
 
 	msk->first = NULL;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 426ed80fe72f..0f0c026c5f8b 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -296,9 +296,17 @@ static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
 	return (struct mptcp_sock *)sk;
 }
 
+/* the msk socket don't use the backlog, also account for the bulk
+ * free memory
+ */
+static inline int __mptcp_rmem(const struct sock *sk)
+{
+	return atomic_read(&sk->sk_rmem_alloc) - READ_ONCE(mptcp_sk(sk)->rmem_released);
+}
+
 static inline int __mptcp_space(const struct sock *sk)
 {
-	return tcp_space(sk) + READ_ONCE(mptcp_sk(sk)->rmem_released);
+	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - __mptcp_rmem(sk));
 }
 
 static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk)
-- 
2.32.0

Re: [PATCH net 0/6] mptcp: Connection and accounting fixes

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Fri,  9 Jul 2021 17:20:45 -0700 you wrote:
> Here are some miscellaneous fixes for MPTCP:
> 
> Patch 1 modifies an MPTCP hash so it doesn't depend on one of skb->dev
> and skb->sk being non-NULL.
> 
> Patch 2 removes an extra destructor call when rejecting a join due to
> port mismatch.
> 
> [...]

Here is the summary with links:
  - [net,1/6] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
    https://git.kernel.org/netdev/net/c/0c71929b5893
  - [net,2/6] mptcp: remove redundant req destruct in subflow_check_req()
    https://git.kernel.org/netdev/net/c/030d37bd1cd2
  - [net,3/6] mptcp: fix syncookie process if mptcp can not_accept new subflow
    https://git.kernel.org/netdev/net/c/8547ea5f52dd
  - [net,4/6] mptcp: avoid processing packet if a subflow reset
    https://git.kernel.org/netdev/net/c/6787b7e350d3
  - [net,5/6] selftests: mptcp: fix case multiple subflows limited by server
    https://git.kernel.org/netdev/net/c/a7da441621c7
  - [net,6/6] mptcp: properly account bulk freed memory
    https://git.kernel.org/netdev/net/c/ce599c516386

You are awesome, thank you!
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