[PATCH AUTOSEL 5.15 07/12] net: annotate data-races around sk->sk_tx_queue_mapping

[Sasha Levin]

From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit 0bb4d124d34044179b42a769a0c76f389ae973b6 ]

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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 include/net/sock.h | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 640bd7a367779..d148dc95c9e9c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1923,21 +1923,33 @@ static inline void sk_tx_queue_set(struct sock *sk, int tx_queue)
 	/* sk_tx_queue_mapping accept only upto a 16-bit value */
 	if (WARN_ON_ONCE((unsigned short)tx_queue >= USHRT_MAX))
 		return;
-	sk->sk_tx_queue_mapping = tx_queue;
+	/* Paired with READ_ONCE() in sk_tx_queue_get() and
+	 * other WRITE_ONCE() because socket lock might be not held.
+	 */
+	WRITE_ONCE(sk->sk_tx_queue_mapping, tx_queue);
 }
 
 #define NO_QUEUE_MAPPING	USHRT_MAX
 
 static inline void sk_tx_queue_clear(struct sock *sk)
 {
-	sk->sk_tx_queue_mapping = NO_QUEUE_MAPPING;
+	/* Paired with READ_ONCE() in sk_tx_queue_get() and
+	 * other WRITE_ONCE() because socket lock might be not held.
+	 */
+	WRITE_ONCE(sk->sk_tx_queue_mapping, NO_QUEUE_MAPPING);
 }
 
 static inline int sk_tx_queue_get(const struct sock *sk)
 {
-	if (sk && sk->sk_tx_queue_mapping != NO_QUEUE_MAPPING)
-		return sk->sk_tx_queue_mapping;
+	if (sk) {
+		/* Paired with WRITE_ONCE() in sk_tx_queue_clear()
+		 * and sk_tx_queue_set().
+		 */
+		int val = READ_ONCE(sk->sk_tx_queue_mapping);
 
+		if (val != NO_QUEUE_MAPPING)
+			return val;
+	}
 	return -1;
 }
 
-- 
2.42.0