netdev - [PATCH net-next 8/8] net: annotate data-races around sk->sk_dst_pending

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Message-ID: <20230921202818.2356959-9-edumazet@google.com>
Date: Thu, 21 Sep 2023 20:28:18 +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 8/8] net: annotate data-races around sk->sk_dst_pending_confirm

This field can be read or written without socket lock being held.

Add annotations to avoid load-store tearing.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sock.h    | 6 +++---
 net/core/sock.c       | 2 +-
 net/ipv4/tcp_output.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index f33e733167df8c2da9240f4af5ed7d715f347394..e70afdb4d29b680aa1081f2b57bab60700b56f5f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2182,7 +2182,7 @@ static inline void __dst_negative_advice(struct sock *sk)
 		if (ndst != dst) {
 			rcu_assign_pointer(sk->sk_dst_cache, ndst);
 			sk_tx_queue_clear(sk);
-			sk->sk_dst_pending_confirm = 0;
+			WRITE_ONCE(sk->sk_dst_pending_confirm, 0);
 		}
 	}
 }
@@ -2199,7 +2199,7 @@ __sk_dst_set(struct sock *sk, struct dst_entry *dst)
 	struct dst_entry *old_dst;
 
 	sk_tx_queue_clear(sk);
-	sk->sk_dst_pending_confirm = 0;
+	WRITE_ONCE(sk->sk_dst_pending_confirm, 0);
 	old_dst = rcu_dereference_protected(sk->sk_dst_cache,
 					    lockdep_sock_is_held(sk));
 	rcu_assign_pointer(sk->sk_dst_cache, dst);
@@ -2212,7 +2212,7 @@ sk_dst_set(struct sock *sk, struct dst_entry *dst)
 	struct dst_entry *old_dst;
 
 	sk_tx_queue_clear(sk);
-	sk->sk_dst_pending_confirm = 0;
+	WRITE_ONCE(sk->sk_dst_pending_confirm, 0);
 	old_dst = xchg((__force struct dst_entry **)&sk->sk_dst_cache, dst);
 	dst_release(old_dst);
 }
diff --git a/net/core/sock.c b/net/core/sock.c
index f0930f858714b6efdb5b4168d7eb5135f65aded4..290165954379292782a484d378a865cc52ca6753 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -600,7 +600,7 @@ struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie)
 	    INDIRECT_CALL_INET(dst->ops->check, ip6_dst_check, ipv4_dst_check,
 			       dst, cookie) == NULL) {
 		sk_tx_queue_clear(sk);
-		sk->sk_dst_pending_confirm = 0;
+		WRITE_ONCE(sk->sk_dst_pending_confirm, 0);
 		RCU_INIT_POINTER(sk->sk_dst_cache, NULL);
 		dst_release(dst);
 		return NULL;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 696dfd64c8c5ffaef43f0f33c9402df2f673dcd3..a13779b24a6c18419836651f82352b324f1dec57 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1325,7 +1325,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 	skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree;
 	refcount_add(skb->truesize, &sk->sk_wmem_alloc);
 
-	skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm);
+	skb_set_dst_pending_confirm(skb, READ_ONCE(sk->sk_dst_pending_confirm));
 
 	/* Build TCP header and checksum it. */
 	th = (struct tcphdr *)skb->data;
-- 
2.42.0.515.g380fc7ccd1-goog