tcp: annotate tp->snd_nxt lockless reads

There are few places where we fetch tp->snd_nxt while
this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make
sure write sides use corresponding WRITE_ONCE() to avoid
store-tearing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 96dd65cbeb85..652568750cb1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -625,7 +625,8 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
                 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
                         answ = 0;
                 else
-                        answ = READ_ONCE(tp->write_seq) - tp->snd_nxt;
+                        answ = READ_ONCE(tp->write_seq) -
+                               READ_ONCE(tp->snd_nxt);
                 break;
         default:
                 return -ENOIOCTLCMD;