tcp: annotate data-race around challenge_timestamp

challenge_timestamp can be read an written by concurrent threads.

This was expected, but we need to annotate the race to avoid potential issues.

Following patch moves challenge_timestamp and challenge_count
to per-netns storage to provide better isolation.

Fixes: 354e4aa391ed ("tcp: RFC 5961 5.2 Blind Data Injection Attack Mitigation")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ab5f0ea..c184e15 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3629,11 +3629,11 @@ static void tcp_send_challenge_ack(struct sock *sk)
 
        /* Then check host-wide RFC 5961 rate limit. */
        now = jiffies / HZ;
-       if (now != challenge_timestamp) {
+       if (now != READ_ONCE(challenge_timestamp)) {
                u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit);
                u32 half = (ack_limit + 1) >> 1;
 
-               challenge_timestamp = now;
+               WRITE_ONCE(challenge_timestamp, now);
                WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit));
        }
        count = READ_ONCE(challenge_count);