Commit 91ecfbcd authored Aug 30, 2022 by Eric Dumazet Committed by Greg Kroah-Hartman Sep 15, 2022

tcp: annotate data-race around challenge_timestamp



[ 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: 354e4aa3 ("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>

parent f8a94fdf

net/ipv4/tcp_input.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -3484,11 +3484,11 @@ 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);