tcp: Fix a data-race around sysctl_tcp_tw_reuse.

[ Upstream commit cbfc6495586a3f09f6f07d9fb3c7cafe807e3c55 ]

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
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>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 32c60122db9c8042cc1560fd666c69aa19184188..d5f13ff7d9004ef183d56b419e78672ed37767d5 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -106,10 +106,10 @@ static u32 tcp_v4_init_ts_off(const struct net *net, const struct sk_buff *skb)
 
 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
 {
+       int reuse = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tw_reuse);
        const struct inet_timewait_sock *tw = inet_twsk(sktw);
        const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
        struct tcp_sock *tp = tcp_sk(sk);
-       int reuse = sock_net(sk)->ipv4.sysctl_tcp_tw_reuse;
 
        if (reuse == 2) {
                /* Still does not detect *everything* that goes through