Commit 998127cd authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: annotate data races in __tcp_oow_rate_limited() 



request sockets are lockless, __tcp_oow_rate_limited() could be called
on the same object from different cpus. This is harmless.

Add READ_ONCE()/WRITE_ONCE() annotations to avoid a KCSAN report.

Fixes: 4ce7e93c ("tcp: rate limit ACK sent by SYN_RECV request sockets")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c94683ed

net/ipv4/tcp_input.c

+9 −3
Original line number Diff line number Diff line
@@ -3590,8 +3590,11 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 
static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,

				   u32 *last_oow_ack_time)

{

	if (*last_oow_ack_time) {

		s32 elapsed = (s32)(tcp_jiffies32 - *last_oow_ack_time);

	/* Paired with the WRITE_ONCE() in this function. */

	u32 val = READ_ONCE(*last_oow_ack_time);



	if (val) {

		s32 elapsed = (s32)(tcp_jiffies32 - val);



		if (0 <= elapsed &&

		    elapsed < READ_ONCE(net->ipv4.sysctl_tcp_invalid_ratelimit)) {
@@ -3600,7 +3603,10 @@ static bool __tcp_oow_rate_limited(struct net *net, int mib_idx, 
		}

	}



	*last_oow_ack_time = tcp_jiffies32;

	/* Paired with the prior READ_ONCE() and with itself,

	 * as we might be lockless.

	 */

	WRITE_ONCE(*last_oow_ack_time, tcp_jiffies32);



	return false;	/* not rate-limited: go ahead, send dupack now! */

}