[PATCH 5.4 24/34] tcp: Fix a data-race around sysctl_tcp_comp_sack_nr.

Greg Kroah-Hartman
2022-08-01T11:49:49Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 79f55473bfc8ac51bd6572929a679eeb4da22251 ]

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

Fixes: 9c21d2fc41c0 ("tcp: add tcp_comp_sack_nr sysctl")
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_input.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f8fa036cfae2..f4e00ff909da 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5303,7 +5303,7 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
}

if (!tcp_is_sack(tp) ||
- tp->compressed_ack >= sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr)
+ tp->compressed_ack >= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_nr))
goto send_now;

if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {
--
2.35.1