tcp: annotate data-race around challenge_timestamp

BugLink: https://bugs.launchpad.net/bugs/1991840
[ Upstream commit 8c70521238b7863c2af607e20bcba20f974c969b ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a33e6aa42a4c51956d3fc7f237b69d8667df782f..7fd7e7cba0c92ea00626772f7e64d9a82dd0f31a 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3623,11 +3623,11 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
 
        /* 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);