tcp: annotate data-races around tp->keepalive_time

do_tcp_getsockopt() reads tp->keepalive_time while another cpu
might change its value.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719212857.3943972-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 226bce6d1e8c30185260baadec449b67323db91c..9e1c3337cdfea61470f2b8f47cec8384aae1b490 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1517,9 +1517,12 @@ static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 static inline int keepalive_time_when(const struct tcp_sock *tp)
 {
        struct net *net = sock_net((struct sock *)tp);
+       int val;
 
-       return tp->keepalive_time ? :
-               READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
+       /* Paired with WRITE_ONCE() in tcp_sock_set_keepidle_locked() */
+       val = READ_ONCE(tp->keepalive_time);
+
+       return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
 }
 
 static inline int keepalive_probes(const struct tcp_sock *tp)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 03ae6554c78d1e42894a8e511cef362134660aac..b4f7856dfb1611f02073699ee24d48f1a6fe7b87 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3312,7 +3312,8 @@ int tcp_sock_set_keepidle_locked(struct sock *sk, int val)
        if (val < 1 || val > MAX_TCP_KEEPIDLE)
                return -EINVAL;
 
-       tp->keepalive_time = val * HZ;
+       /* Paired with WRITE_ONCE() in keepalive_time_when() */
+       WRITE_ONCE(tp->keepalive_time, val * HZ);
        if (sock_flag(sk, SOCK_KEEPOPEN) &&
            !((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))) {
                u32 elapsed = keepalive_time_elapsed(tp);