netdev - [PATCH net 02/11] net: annotate data-race around sk->sk

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Date: Fri, 28 Jul 2023 15:03:09 +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: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, 
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Akhmat Karakotov <hmukos@...dex-team.ru>
Subject: [PATCH net 02/11] net: annotate data-race around sk->sk_txrehash

sk_getsockopt() runs locklessly. This means sk->sk_txrehash
can be read while other threads are changing its value.

Other locations were handled in commit cb6cd2cec799
("tcp: Change SYN ACK retransmit behaviour to account for rehash")

Fixes: 26859240e4ee ("txhash: Add socket option to control TX hash rethink behavior")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Akhmat Karakotov <hmukos@...dex-team.ru>
---
 net/core/sock.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index bd201d15e72aad4ea0b11941eaaa992de706634a..adec93dda56af7314f4a63c77f3848441f0d41ae 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1534,7 +1534,9 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 		}
 		if ((u8)val == SOCK_TXREHASH_DEFAULT)
 			val = READ_ONCE(sock_net(sk)->core.sysctl_txrehash);
-		/* Paired with READ_ONCE() in tcp_rtx_synack() */
+		/* Paired with READ_ONCE() in tcp_rtx_synack()
+		 * and sk_getsockopt().
+		 */
 		WRITE_ONCE(sk->sk_txrehash, (u8)val);
 		break;
 
@@ -1978,7 +1980,8 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_TXREHASH:
-		v.val = sk->sk_txrehash;
+		/* Paired with WRITE_ONCE() in sk_setsockopt() */
+		v.val = READ_ONCE(sk->sk_txrehash);
 		break;
 
 	default:
-- 
2.41.0.585.gd2178a4bd4-goog