net: annotate data-races around sk->sk_bind_phc

sk->sk_bind_phc is read locklessly. Add corresponding annotations.

Fixes: d463126 ("net: sock: extend SO_TIMESTAMPING for PHC binding")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: edumazet

net/core/sock.c

@@ -894,7 +894,7 @@ static int sock_timestamping_bind_phc(struct sock *sk, int phc_index)
 	if (!match)
 		return -EINVAL;
 
-	sk->sk_bind_phc = phc_index;
+	WRITE_ONCE(sk->sk_bind_phc, phc_index);
 
 	return 0;
 }
@@ -1720,7 +1720,7 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 	case SO_TIMESTAMPING_OLD:
 		lv = sizeof(v.timestamping);
 		v.timestamping.flags = READ_ONCE(sk->sk_tsflags);
-		v.timestamping.bind_phc = sk->sk_bind_phc;
+		v.timestamping.bind_phc = READ_ONCE(sk->sk_bind_phc);
 		break;
 
 	case SO_RCVTIMEO_OLD:

net/socket.c

@@ -939,7 +939,7 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 
 		if (tsflags & SOF_TIMESTAMPING_BIND_PHC)
 			hwtstamp = ptp_convert_timestamp(&hwtstamp,
-							 sk->sk_bind_phc);
+							 READ_ONCE(sk->sk_bind_phc));
 
 		if (ktime_to_timespec64_cond(hwtstamp, tss.ts + 2)) {
 			empty = 0;