[PATCH 5.15 27/69] tcp: Fix a data-race around sysctl_tcp_challenge_ack_limit.

Greg Kroah-Hartman
2022-08-01T12:03:09Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

commit db3815a2fa691da145cfbe834584f31ad75df9ff upstream.

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

Fixes: 282f23c6ee34 ("tcp: implement RFC 5961 3.2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_input.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3622,7 +3622,7 @@ static void tcp_send_challenge_ack(struc
/* Then check host-wide RFC 5961 rate limit. */
now = jiffies / HZ;
if (now != challenge_timestamp) {
- u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit;
+ u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit);
u32 half = (ack_limit + 1) >> 1;

challenge_timestamp = now;