Merge branch 'tcp-annotate-data-races-in-tcp_rsk-req'

Eric Dumazet says:

====================
tcp: annotate data-races in tcp_rsk(req)

Small series addressing two syzbot reports around tcp_rsk(req)
====================

Link: https://lore.kernel.org/r/20230717144445.653164-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/ipv4/tcp_ipv4.c

@@ -988,11 +988,12 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_rsk(req)->rcv_nxt,
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
 			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
-			req->ts_recent,
+			READ_ONCE(req->ts_recent),
 			0,
 			tcp_md5_do_lookup(sk, l3index, addr, AF_INET),
 			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
-			ip_hdr(skb)->tos, tcp_rsk(req)->txhash);
+			ip_hdr(skb)->tos,
+			READ_ONCE(tcp_rsk(req)->txhash));
 }
 
 /*

net/ipv4/tcp_minisocks.c

@@ -528,7 +528,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 	newicsk->icsk_ack.lrcvtime = tcp_jiffies32;
 
 	newtp->lsndtime = tcp_jiffies32;
-	newsk->sk_txhash = treq->txhash;
+	newsk->sk_txhash = READ_ONCE(treq->txhash);
 	newtp->total_retrans = req->num_retrans;
 
 	tcp_init_xmit_timers(newsk);
@@ -555,7 +555,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 	newtp->max_window = newtp->snd_wnd;
 
 	if (newtp->rx_opt.tstamp_ok) {
-		newtp->rx_opt.ts_recent = req->ts_recent;
+		newtp->rx_opt.ts_recent = READ_ONCE(req->ts_recent);
 		newtp->rx_opt.ts_recent_stamp = ktime_get_seconds();
 		newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
 	} else {
@@ -619,7 +619,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 		tcp_parse_options(sock_net(sk), skb, &tmp_opt, 0, NULL);
 
 		if (tmp_opt.saw_tstamp) {
-			tmp_opt.ts_recent = req->ts_recent;
+			tmp_opt.ts_recent = READ_ONCE(req->ts_recent);
 			if (tmp_opt.rcv_tsecr)
 				tmp_opt.rcv_tsecr -= tcp_rsk(req)->ts_off;
 			/* We do not store true stamp, but it is not required,
@@ -758,8 +758,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 
 	/* In sequence, PAWS is OK. */
 
+	/* TODO: We probably should defer ts_recent change once
+	 * we take ownership of @req.
+	 */
 	if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
-		req->ts_recent = tmp_opt.rcv_tsval;
+		WRITE_ONCE(req->ts_recent, tmp_opt.rcv_tsval);
 
 	if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
 		/* Truncate SYN, it is out of window starting

net/ipv4/tcp_output.c

@@ -878,7 +878,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
 	if (likely(ireq->tstamp_ok)) {
 		opts->options |= OPTION_TS;
 		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
-		opts->tsecr = req->ts_recent;
+		opts->tsecr = READ_ONCE(req->ts_recent);
 		remaining -= TCPOLEN_TSTAMP_ALIGNED;
 	}
 	if (likely(ireq->sack_ok)) {
@@ -3660,7 +3660,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 	rcu_read_lock();
 	md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
 #endif
-	skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4);
+	skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);
 	/* bpf program will be interested in the tcp_flags */
 	TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
 	tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
@@ -4210,7 +4210,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 
 	/* Paired with WRITE_ONCE() in sock_setsockopt() */
 	if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
-		tcp_rsk(req)->txhash = net_tx_rndhash();
+		WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash());
 	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
 				  NULL);
 	if (!res) {

net/ipv6/tcp_ipv6.c

@@ -1126,10 +1126,10 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_rsk(req)->rcv_nxt,
 			req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
 			tcp_time_stamp_raw() + tcp_rsk(req)->ts_off,
-			req->ts_recent, sk->sk_bound_dev_if,
+			READ_ONCE(req->ts_recent), sk->sk_bound_dev_if,
 			tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr, l3index),
 			ipv6_get_dsfield(ipv6_hdr(skb)), 0, sk->sk_priority,
-			tcp_rsk(req)->txhash);
+			READ_ONCE(tcp_rsk(req)->txhash));
 }