tcp: annotate data-races around tp->keepalive_intvl

do_tcp_getsockopt() reads tp->keepalive_intvl 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/20230719212857.3943972-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 9e1c333..2d8d58d 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1509,9 +1509,14 @@ void tcp_leave_memory_pressure(struct sock *sk);
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 {
        struct net *net = sock_net((struct sock *)tp);
+       int val;
+
+       /* Paired with WRITE_ONCE() in tcp_sock_set_keepintvl()
+        * and do_tcp_setsockopt().
+        */
+       val = READ_ONCE(tp->keepalive_intvl);
 
-       return tp->keepalive_intvl ? :
-               READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
+       return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
 }
 
 static inline int keepalive_time_when(const struct tcp_sock *tp)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b4f7856..d55fe01 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3345,7 +3345,7 @@ int tcp_sock_set_keepintvl(struct sock *sk, int val)
                return -EINVAL;
 
        lock_sock(sk);
-       tcp_sk(sk)->keepalive_intvl = val * HZ;
+       WRITE_ONCE(tcp_sk(sk)->keepalive_intvl, val * HZ);
        release_sock(sk);
        return 0;
 }
@@ -3559,7 +3559,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
                if (val < 1 || val > MAX_TCP_KEEPINTVL)
                        err = -EINVAL;
                else
-                       tp->keepalive_intvl = val * HZ;
+                       WRITE_ONCE(tp->keepalive_intvl, val * HZ);
                break;
        case TCP_KEEPCNT:
                if (val < 1 || val > MAX_TCP_KEEPCNT)