tcp: Fix a data-race around sysctl_tcp_limit_output_bytes.

While reading sysctl_tcp_limit_output_bytes, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its reader.

Fixes: 6475c3971092 ("tcp: TCP Small Queues")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 88f7d51e66914037e4a2e63a4fbf0ebf1ecc8d41..80c9bed733372779431c482ad9b65f155588deca 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2507,7 +2507,7 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
                      sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));
        if (sk->sk_pacing_status == SK_PACING_NONE)
                limit = min_t(unsigned long, limit,
-                             sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);
+                             READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes));
        limit <<= factor;
 
        if (static_branch_unlikely(&tcp_tx_delay_enabled) &&