[PATCH 5.10 36/65] tcp: Fix a data-race around sysctl_tcp_comp_sack_delay_ns.

Greg Kroah-Hartman
2022-08-01T11:59:13Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 4866b2b0f7672b6d760c4b8ece6fb56f965dcc8a ]

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

Fixes: 6d82aa242092 ("tcp: add tcp_comp_sack_delay_ns 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 | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 716bc95ebfb0..b86d98c07cdf 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5461,7 +5461,8 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
if (tp->srtt_us && tp->srtt_us < rtt)
rtt = tp->srtt_us;

- delay = min_t(unsigned long, sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns,
+ delay = min_t(unsigned long,
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_delay_ns),
rtt * (NSEC_PER_USEC >> 3)/20);
sock_hold(sk);
hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay),
--
2.35.1