netdev - [PATCH net 08/11] tcp: annotate data-races around rskq_defer

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Date: Wed, 19 Jul 2023 21:28:54 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 08/11] tcp: annotate data-races around rskq_defer_accept

do_tcp_getsockopt() reads rskq_defer_accept while another cpu
might change its value.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2cf129a0c00bfef813e1f1e12cb247ef8107fa88..5beec71a5c418db65e19eb2a68ffd839d4550efc 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3594,9 +3594,9 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 
 	case TCP_DEFER_ACCEPT:
 		/* Translate value in seconds to number of retransmits */
-		icsk->icsk_accept_queue.rskq_defer_accept =
-			secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ,
-					TCP_RTO_MAX / HZ);
+		WRITE_ONCE(icsk->icsk_accept_queue.rskq_defer_accept,
+			   secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ,
+					   TCP_RTO_MAX / HZ));
 		break;
 
 	case TCP_WINDOW_CLAMP:
@@ -4002,8 +4002,9 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 			val = (val ? : READ_ONCE(net->ipv4.sysctl_tcp_fin_timeout)) / HZ;
 		break;
 	case TCP_DEFER_ACCEPT:
-		val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,
-				      TCP_TIMEOUT_INIT / HZ, TCP_RTO_MAX / HZ);
+		val = READ_ONCE(icsk->icsk_accept_queue.rskq_defer_accept);
+		val = retrans_to_secs(val, TCP_TIMEOUT_INIT / HZ,
+				      TCP_RTO_MAX / HZ);
 		break;
 	case TCP_WINDOW_CLAMP:
 		val = tp->window_clamp;
-- 
2.41.0.255.g8b1d071c50-goog