[PATCH 5.18 042/158] tcp: Fix data-races around sysctl_tcp_mtu_probing.

Greg Kroah-Hartman
2022-07-27T17:33:31Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit f47d00e077e7d61baf69e46dde3210c886360207 ]

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

Fixes: 5d424d5a674f ("[TCP]: MTU probing")
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_output.c | 2 +-
net/ipv4/tcp_timer.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 34249469e361..f0f2e1aea8c7 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1760,7 +1760,7 @@ void tcp_mtup_init(struct sock *sk)
struct inet_connection_sock *icsk = inet_csk(sk);
struct net *net = sock_net(sk);

- icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
+ icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;
icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
icsk->icsk_af_ops->net_header_len;
icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 20cf4a98c69d..98bb00e29e1e 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -163,7 +163,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
int mss;

/* Black hole detection */
- if (!net->ipv4.sysctl_tcp_mtu_probing)
+ if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing))
return;

if (!icsk->icsk_mtup.enabled) {
--
2.35.1