dccp: annotate lockless accesses to sk->sk_err_soft

This field can be read/written without lock synchronization.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dccp/ipv4.c

@@ -177,7 +177,7 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
 	 * for the case, if this connection will not able to recover.
 	 */
 	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
-		sk->sk_err_soft = EMSGSIZE;
+		WRITE_ONCE(sk->sk_err_soft, EMSGSIZE);
 
 	mtu = dst_mtu(dst);
 
@@ -339,8 +339,9 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
 			sk_error_report(sk);
 
 			dccp_done(sk);
-		} else
-			sk->sk_err_soft = err;
+		} else {
+			WRITE_ONCE(sk->sk_err_soft, err);
+		}
 		goto out;
 	}
 
@@ -364,8 +365,9 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
 	if (!sock_owned_by_user(sk) && inet->recverr) {
 		sk->sk_err = err;
 		sk_error_report(sk);
-	} else /* Only an error on timeout */
-		sk->sk_err_soft = err;
+	} else { /* Only an error on timeout */
+		WRITE_ONCE(sk->sk_err_soft, err);
+	}
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);

net/dccp/ipv6.c

@@ -174,17 +174,18 @@ static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 			 */
 			sk_error_report(sk);
 			dccp_done(sk);
-		} else
-			sk->sk_err_soft = err;
+		} else {
+			WRITE_ONCE(sk->sk_err_soft, err);
+		}
 		goto out;
 	}
 
 	if (!sock_owned_by_user(sk) && np->recverr) {
 		sk->sk_err = err;
 		sk_error_report(sk);
-	} else
-		sk->sk_err_soft = err;
-
+	} else {
+		WRITE_ONCE(sk->sk_err_soft, err);
+	}
 out:
 	bh_unlock_sock(sk);
 	sock_put(sk);

net/dccp/timer.c

@@ -19,7 +19,7 @@ int  sysctl_dccp_retries2		__read_mostly = TCP_RETR2;
 
 static void dccp_write_err(struct sock *sk)
 {
-	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
+	sk->sk_err = READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT;
 	sk_error_report(sk);
 
 	dccp_send_reset(sk, DCCP_RESET_CODE_ABORTED);