[PATCH 5.4 38/87] tcp: Fix data-races around sysctl_tcp_fastopen.

Greg Kroah-Hartman
2022-07-27T16:41:16Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 5a54213318c43f4009ae158347aa6016e3b9b55a ]

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

Fixes: 2100c8d2d9db ("net-tcp: Fast Open base")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/af_inet.c | 2 +-
net/ipv4/tcp.c | 6 ++++--
net/ipv4/tcp_fastopen.c | 4 ++--
3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 06153386776d..d61ca7be6eda 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -219,7 +219,7 @@ int inet_listen(struct socket *sock, int backlog)
* because the socket was in TCP_LISTEN state previously but
* was shutdown() rather than close().
*/
- tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
+ tcp_fastopen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen);
if ((tcp_fastopen & TFO_SERVER_WO_SOCKOPT1) &&
(tcp_fastopen & TFO_SERVER_ENABLE) &&
!inet_csk(sk)->icsk_accept_queue.fastopenq.max_qlen) {
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 333d221e0717..4b31f6e9ec61 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1148,7 +1148,8 @@ static int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
struct sockaddr *uaddr = msg->msg_name;
int err, flags;

- if (!(sock_net(sk)->ipv4.sysctl_tcp_fastopen & TFO_CLIENT_ENABLE) ||
+ if (!(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen) &
+ TFO_CLIENT_ENABLE) ||
(uaddr && msg->msg_namelen >= sizeof(uaddr->sa_family) &&
uaddr->sa_family == AF_UNSPEC))
return -EOPNOTSUPP;
@@ -3127,7 +3128,8 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
case TCP_FASTOPEN_CONNECT:
if (val > 1 || val < 0) {
err = -EINVAL;
- } else if (net->ipv4.sysctl_tcp_fastopen & TFO_CLIENT_ENABLE) {
+ } else if (READ_ONCE(net->ipv4.sysctl_tcp_fastopen) &
+ TFO_CLIENT_ENABLE) {
if (sk->sk_state == TCP_CLOSE)
tp->fastopen_connect = val;
else
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index a5ec77a5ad6f..21705b2ddaff 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -349,7 +349,7 @@ static bool tcp_fastopen_no_cookie(const struct sock *sk,
const struct dst_entry *dst,
int flag)
{
- return (sock_net(sk)->ipv4.sysctl_tcp_fastopen & flag) ||
+ return (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen) & flag) ||
tcp_sk(sk)->fastopen_no_cookie ||
(dst && dst_metric(dst, RTAX_FASTOPEN_NO_COOKIE));
}
@@ -364,7 +364,7 @@ struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
const struct dst_entry *dst)
{
bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
- int tcp_fastopen = sock_net(sk)->ipv4.sysctl_tcp_fastopen;
+ int tcp_fastopen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen);
struct tcp_fastopen_cookie valid_foc = { .len = -1 };
struct sock *child;
int ret = 0;
--
2.35.1