tcp: annotate data-races in tcp_req_diag_fill()

req->num_retrans and rsk_timer.expires are read locklessly,
and can be changed from tcp_rtx_synack().

Add READ_ONCE()/WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: edumazet

net/ipv4/tcp_diag.c

@@ -248,12 +248,12 @@ static int tcp_req_diag_fill(struct sock *sk, struct sk_buff *skb,
 	inet_diag_msg_common_fill(r, sk);
 	r->idiag_state = TCP_SYN_RECV;
 	r->idiag_timer = 1;
-	r->idiag_retrans = reqsk->num_retrans;
+	r->idiag_retrans = READ_ONCE(reqsk->num_retrans);
 
 	BUILD_BUG_ON(offsetof(struct inet_request_sock, ir_cookie) !=
 		     offsetof(struct sock, sk_cookie));
 
-	tmo = inet_reqsk(sk)->rsk_timer.expires - jiffies;
+	tmo = READ_ONCE(inet_reqsk(sk)->rsk_timer.expires) - jiffies;
 	r->idiag_expires = jiffies_delta_to_msecs(tmo);
 	r->idiag_rqueue	= 0;
 	r->idiag_wqueue	= 0;

net/ipv4/tcp_output.c

@@ -4438,7 +4438,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 			tcp_sk_rw(sk)->total_retrans++;
 		}
 		trace_tcp_retransmit_synack(sk, req);
-		req->num_retrans++;
+		WRITE_ONCE(req->num_retrans, req->num_retrans + 1);
 	}
 	return res;
 }