tcp: Fix a data-race around sysctl_tcp_comp_sack_slack_ns.

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>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 813744180d87920a5e5c88c9550b00cdcebca8a3..a4d8851d83ff60b88c0f32f00212e3fb6d921e05 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5547,7 +5547,7 @@ 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);
 }