tcp: tcp_get_info() should fetch socket fields once

tcp_get_info() can be called without holding socket lock,
so any socket fields can change under us.

Use READ_ONCE() to fetch sk_pacing_rate and sk_max_pacing_rate

Fixes: 977cb0ecf82e ("tcp: add pacing_rate information into tcp_info")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 18e3a12..59c8a02 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2595,6 +2595,7 @@ void tcp_get_info(const struct sock *sk, struct tcp_info *info)
        const struct tcp_sock *tp = tcp_sk(sk);
        const struct inet_connection_sock *icsk = inet_csk(sk);
        u32 now = tcp_time_stamp;
+       u32 rate;
 
        memset(info, 0, sizeof(*info));
 
@@ -2655,10 +2656,11 @@ void tcp_get_info(const struct sock *sk, struct tcp_info *info)
 
        info->tcpi_total_retrans = tp->total_retrans;
 
-       info->tcpi_pacing_rate = sk->sk_pacing_rate != ~0U ?
-                                       sk->sk_pacing_rate : ~0ULL;
-       info->tcpi_max_pacing_rate = sk->sk_max_pacing_rate != ~0U ?
-                                       sk->sk_max_pacing_rate : ~0ULL;
+       rate = READ_ONCE(sk->sk_pacing_rate);
+       info->tcpi_pacing_rate = rate != ~0U ? rate : ~0ULL;
+
+       rate = READ_ONCE(sk->sk_max_pacing_rate);
+       info->tcpi_max_pacing_rate = rate != ~0U ? rate : ~0ULL;
 }
 EXPORT_SYMBOL_GPL(tcp_get_info);