[PATCH 6/7] net/tcp: ACCESS_ONCE() on snd/rcv SNEs

[Dmitry Safonov <dima@arista.com>]

SNEs need READ_ONCE()/WRITE_ONCE() for access as they can be written and
read at the same time.

This is actually a shame: I planned to send it in TCP-AO patches, but
it seems I've chosen a wrong commit to git-commit-fixup some time ago.
It ended up in a commit that adds a selftest. Human factor.

Fixes: 64382c71a557 ("net/tcp: Add TCP-AO SNE support")
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 net/ipv4/tcp_ao.c    | 4 ++--
 net/ipv4/tcp_input.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 122ff58168ee..9b7f1970c2e9 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -956,8 +956,8 @@ tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb,
 		if (unlikely(th->syn && !th->ack))
 			goto verify_hash;
 
-		sne = tcp_ao_compute_sne(info->rcv_sne, tcp_sk(sk)->rcv_nxt,
-					 ntohl(th->seq));
+		sne = tcp_ao_compute_sne(READ_ONCE(info->rcv_sne),
+					 tcp_sk(sk)->rcv_nxt, ntohl(th->seq));
 		/* Established socket, traffic key are cached */
 		traffic_key = rcv_other_key(key);
 		err = tcp_ao_verify_hash(sk, skb, family, info, aoh, key,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bcb55d98004c..78896c8be0d4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3583,7 +3583,7 @@ static void tcp_snd_sne_update(struct tcp_sock *tp, u32 ack)
 	ao = rcu_dereference_protected(tp->ao_info,
 				       lockdep_sock_is_held((struct sock *)tp));
 	if (ao && ack < tp->snd_una)
-		ao->snd_sne++;
+		WRITE_ONCE(ao->snd_sne, ao->snd_sne + 1);
 #endif
 }
 
@@ -3609,7 +3609,7 @@ static void tcp_rcv_sne_update(struct tcp_sock *tp, u32 seq)
 	ao = rcu_dereference_protected(tp->ao_info,
 				       lockdep_sock_is_held((struct sock *)tp));
 	if (ao && seq < tp->rcv_nxt)
-		ao->rcv_sne++;
+		WRITE_ONCE(ao->rcv_sne, ao->rcv_sne + 1);
 #endif
 }
 
-- 
2.42.0