netdev - [PATCH net-next 5/5] mptcp: annotate lockless accesses around read-mostly fields

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Date: Fri, 02 Feb 2024 12:40:11 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang.tang@...ux.dev>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Subject: [PATCH net-next 5/5] mptcp: annotate lockless accesses around
 read-mostly fields

From: Paolo Abeni <pabeni@...hat.com>

The following MPTCP socket fields:

 - can_ack
 - fully_established
 - rcv_data_fin
 - snd_data_fin_enable
 - rcv_fastclose
 - use_64bit_ack

are accessed without any lock, add the appropriate annotation.

The schema is safe as each field can change its value at most
once in the whole mptcp socket life cycle.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/protocol.c | 14 +++++++-------
 net/mptcp/sockopt.c  |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 4478ddd3b5fa..ad39f54b3a81 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3149,16 +3149,16 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	msk->cb_flags = 0;
 	msk->push_pending = 0;
 	msk->recovery = false;
-	msk->can_ack = false;
-	msk->fully_established = false;
-	msk->rcv_data_fin = false;
-	msk->snd_data_fin_enable = false;
-	msk->rcv_fastclose = false;
-	msk->use_64bit_ack = false;
-	msk->bytes_consumed = 0;
+	WRITE_ONCE(msk->can_ack, false);
+	WRITE_ONCE(msk->fully_established, false);
+	WRITE_ONCE(msk->rcv_data_fin, false);
+	WRITE_ONCE(msk->snd_data_fin_enable, false);
+	WRITE_ONCE(msk->rcv_fastclose, false);
+	WRITE_ONCE(msk->use_64bit_ack, false);
 	WRITE_ONCE(msk->csum_enabled, mptcp_is_checksum_enabled(sock_net(sk)));
 	mptcp_pm_data_reset(msk);
 	mptcp_ca_reset(sk);
+	msk->bytes_consumed = 0;
 	msk->bytes_acked = 0;
 	msk->bytes_received = 0;
 	msk->bytes_sent = 0;
diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c
index c40f1428e602..da37e4541a5d 100644
--- a/net/mptcp/sockopt.c
+++ b/net/mptcp/sockopt.c
@@ -942,7 +942,7 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 	mptcp_data_unlock(sk);
 
 	slow = lock_sock_fast(sk);
-	info->mptcpi_csum_enabled = msk->csum_enabled;
+	info->mptcpi_csum_enabled = READ_ONCE(msk->csum_enabled);
 	info->mptcpi_token = msk->token;
 	info->mptcpi_write_seq = msk->write_seq;
 	info->mptcpi_retransmits = inet_csk(sk)->icsk_retransmits;

-- 
2.43.0