tcp: Fix a data-race around sysctl_tcp_comp_sack_slack_ns.

[ Upstream commit 22396941a7f343d704738360f9ef0e6576489d43 ]

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

Fixes: a70437cc09a1 ("tcp: add hrtimer slack to sack compression")
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>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3591a25a86311e5fbeccb45f1c45a547d0362d57..5de396075a27c447edde15a822553d84b6a72912 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5551,7 +5551,7 @@ send_now:
                      rtt * (NSEC_PER_USEC >> 3)/20);
        sock_hold(sk);
        hrtimer_start_range_ns(&tp->compressed_ack_timer, ns_to_ktime(delay),
-                              sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns,
+                              READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_comp_sack_slack_ns),
                               HRTIMER_MODE_REL_PINNED_SOFT);
 }