tcp: Fix a data-race around sysctl_tcp_autocorking.

[ Upstream commit 85225e6f0a ]

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

Fixes: f54b311142 ("tcp: auto corking")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/ipv4/tcp.c

@@ -694,7 +694,7 @@ static bool tcp_should_autocork(struct sock *sk, struct sk_buff *skb,
 				int size_goal)
 {
 	return skb->len < size_goal &&
-	       sock_net(sk)->ipv4.sysctl_tcp_autocorking &&
+	       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_autocorking) &&
 	       !tcp_rtx_queue_empty(sk) &&
 	       refcount_read(&sk->sk_wmem_alloc) > skb->truesize;
 }