net: annotate data-race around sk->sk_txrehash

sk_getsockopt() runs locklessly. This means sk->sk_txrehash
can be read while other threads are changing its value.

Other locations were handled in commit cb6cd2cec799
("tcp: Change SYN ACK retransmit behaviour to account for rehash")

Fixes: 26859240e4ee ("txhash: Add socket option to control TX hash rethink behavior")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Akhmat Karakotov <hmukos@yandex-team.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/sock.c b/net/core/sock.c
index bd201d1..adec93d 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1534,7 +1534,9 @@ set_sndbuf:
                }
                if ((u8)val == SOCK_TXREHASH_DEFAULT)
                        val = READ_ONCE(sock_net(sk)->core.sysctl_txrehash);
-               /* Paired with READ_ONCE() in tcp_rtx_synack() */
+               /* Paired with READ_ONCE() in tcp_rtx_synack()
+                * and sk_getsockopt().
+                */
                WRITE_ONCE(sk->sk_txrehash, (u8)val);
                break;
 
@@ -1978,7 +1980,8 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
                break;
 
        case SO_TXREHASH:
-               v.val = sk->sk_txrehash;
+               /* Paired with WRITE_ONCE() in sk_setsockopt() */
+               v.val = READ_ONCE(sk->sk_txrehash);
                break;
 
        default: