[PATCH 5.10 056/105] tcp: Fix data-races around sysctl_tcp_fastopen_blackhole_timeout.

Greg Kroah-Hartman
2022-07-27T16:56:05Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 021266ec640c7a4527e6cd4b7349a512b351de1d ]

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

Fixes: cf1ef3f0719b ("net/tcp_fastopen: Disable active side TFO in certain scenarios")
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_fastopen.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index ed7aa6ae7b51..39fb037ce5f3 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -506,7 +506,7 @@ void tcp_fastopen_active_disable(struct sock *sk)
{
struct net *net = sock_net(sk);

- if (!sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout)
+ if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout))
return;

/* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
@@ -527,7 +527,8 @@ void tcp_fastopen_active_disable(struct sock *sk)
*/
bool tcp_fastopen_active_should_disable(struct sock *sk)
{
- unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
+ unsigned int tfo_bh_timeout =
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout);
unsigned long timeout;
int tfo_da_times;
int multiplier;
--
2.35.1