netdev - [PATCH net-next] tcp: annotate data-race around queue->synflood

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Date:   Tue, 15 Nov 2022 09:18:51 +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-next] tcp: annotate data-race around queue->synflood_warned

Annotate the lockless read of queue->synflood_warned.

Following xchg() has the needed data-race resolution.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 94024fdc2da1b28af1b3b6e50735bf6b915f861d..0ae291e53eab228ce171cd73abafc009d99b886d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6841,7 +6841,7 @@ static bool tcp_syn_flood_action(const struct sock *sk, const char *proto)
 #endif
 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
 
-	if (!queue->synflood_warned && syncookies != 2 &&
+	if (!READ_ONCE(queue->synflood_warned) && syncookies != 2 &&
 	    xchg(&queue->synflood_warned, 1) == 0) {
 		if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
 			net_info_ratelimited("%s: Possible SYN flooding on port [%pI6c]:%u. %s.\n",
-- 
2.38.1.431.g37b22c650d-goog