Commit f410cbea authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: annotate data-races around tp->window_clamp 



tp->window_clamp can be read locklessly, add READ_ONCE()
and WRITE_ONCE() annotations.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/r/20240404114231.2195171-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 571faefe

net/ipv4/syncookies.c

+2 −1
Original line number Diff line number Diff line
@@ -462,7 +462,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) 
	}



	/* Try to redo what tcp_v4_send_synack did. */

	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);

	req->rsk_window_clamp = READ_ONCE(tp->window_clamp) ? :

				dst_metric(&rt->dst, RTAX_WINDOW);

	/* limit the window selection if the user enforce a smaller rx buffer */

	full_space = tcp_full_space(sk);

	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&

net/ipv4/tcp.c

+4 −4
Original line number Diff line number Diff line
@@ -1721,7 +1721,7 @@ int tcp_set_rcvlowat(struct sock *sk, int val) 
	space = tcp_space_from_win(sk, val);

	if (space > sk->sk_rcvbuf) {

		WRITE_ONCE(sk->sk_rcvbuf, space);

		tcp_sk(sk)->window_clamp = val;

		WRITE_ONCE(tcp_sk(sk)->window_clamp, val);

	}

	return 0;

}
@@ -3379,7 +3379,7 @@ int tcp_set_window_clamp(struct sock *sk, int val) 
	if (!val) {

		if (sk->sk_state != TCP_CLOSE)

			return -EINVAL;

		tp->window_clamp = 0;

		WRITE_ONCE(tp->window_clamp, 0);

	} else {

		u32 new_rcv_ssthresh, old_window_clamp = tp->window_clamp;

		u32 new_window_clamp = val < SOCK_MIN_RCVBUF / 2 ?
@@ -3388,7 +3388,7 @@ int tcp_set_window_clamp(struct sock *sk, int val) 
		if (new_window_clamp == old_window_clamp)

			return 0;



		tp->window_clamp = new_window_clamp;

		WRITE_ONCE(tp->window_clamp, new_window_clamp);

		if (new_window_clamp < old_window_clamp) {

			/* need to apply the reserved mem provisioning only

			 * when shrinking the window clamp
@@ -4057,7 +4057,7 @@ int do_tcp_getsockopt(struct sock *sk, int level, 
				      TCP_RTO_MAX / HZ);

		break;

	case TCP_WINDOW_CLAMP:

		val = tp->window_clamp;

		val = READ_ONCE(tp->window_clamp);

		break;

	case TCP_INFO: {

		struct tcp_info info;

net/ipv4/tcp_input.c

+10 −7
Original line number Diff line number Diff line
@@ -563,19 +563,20 @@ static void tcp_init_buffer_space(struct sock *sk) 
	maxwin = tcp_full_space(sk);



	if (tp->window_clamp >= maxwin) {

		tp->window_clamp = maxwin;

		WRITE_ONCE(tp->window_clamp, maxwin);



		if (tcp_app_win && maxwin > 4 * tp->advmss)

			tp->window_clamp = max(maxwin -

					       (maxwin >> tcp_app_win),

					       4 * tp->advmss);

			WRITE_ONCE(tp->window_clamp,

				   max(maxwin - (maxwin >> tcp_app_win),

				       4 * tp->advmss));

	}



	/* Force reservation of one segment. */

	if (tcp_app_win &&

	    tp->window_clamp > 2 * tp->advmss &&

	    tp->window_clamp + tp->advmss > maxwin)

		tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);

		WRITE_ONCE(tp->window_clamp,

			   max(2 * tp->advmss, maxwin - tp->advmss));



	tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);

	tp->snd_cwnd_stamp = tcp_jiffies32;
@@ -773,7 +774,8 @@ void tcp_rcv_space_adjust(struct sock *sk) 
			WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);



			/* Make the window clamp follow along.  */

			tp->window_clamp = tcp_win_from_space(sk, rcvbuf);

			WRITE_ONCE(tp->window_clamp,

				   tcp_win_from_space(sk, rcvbuf));

		}

	}

	tp->rcvq_space.space = copied;
@@ -6426,7 +6428,8 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 


		if (!tp->rx_opt.wscale_ok) {

			tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;

			tp->window_clamp = min(tp->window_clamp, 65535U);

			WRITE_ONCE(tp->window_clamp,

				   min(tp->window_clamp, 65535U));

		}



		if (tp->rx_opt.saw_tstamp) {

net/ipv4/tcp_output.c

+10 −8
Original line number Diff line number Diff line
@@ -203,16 +203,17 @@ static inline void tcp_event_ack_sent(struct sock *sk, u32 rcv_nxt) 
 * This MUST be enforced by all callers.

 */

void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss,

			       __u32 *rcv_wnd, __u32 *window_clamp,

			       __u32 *rcv_wnd, __u32 *__window_clamp,

			       int wscale_ok, __u8 *rcv_wscale,

			       __u32 init_rcv_wnd)

{

	unsigned int space = (__space < 0 ? 0 : __space);

	u32 window_clamp = READ_ONCE(*__window_clamp);



	/* If no clamp set the clamp to the max possible scaled window */

	if (*window_clamp == 0)

		(*window_clamp) = (U16_MAX << TCP_MAX_WSCALE);

	space = min(*window_clamp, space);

	if (window_clamp == 0)

		window_clamp = (U16_MAX << TCP_MAX_WSCALE);

	space = min(window_clamp, space);



	/* Quantize space offering to a multiple of mss if possible. */

	if (space > mss)
@@ -239,12 +240,13 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss, 
		/* Set window scaling on max possible window */

		space = max_t(u32, space, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));

		space = max_t(u32, space, READ_ONCE(sysctl_rmem_max));

		space = min_t(u32, space, *window_clamp);

		space = min_t(u32, space, window_clamp);

		*rcv_wscale = clamp_t(int, ilog2(space) - 15,

				      0, TCP_MAX_WSCALE);

	}

	/* Set the clamp no higher than max representable value */

	(*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);

	WRITE_ONCE(*__window_clamp,

		   min_t(__u32, U16_MAX << (*rcv_wscale), window_clamp));

}

EXPORT_SYMBOL(tcp_select_initial_window);
@@ -3855,7 +3857,7 @@ static void tcp_connect_init(struct sock *sk) 
	tcp_ca_dst_init(sk, dst);



	if (!tp->window_clamp)

		tp->window_clamp = dst_metric(dst, RTAX_WINDOW);

		WRITE_ONCE(tp->window_clamp, dst_metric(dst, RTAX_WINDOW));

	tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst));



	tcp_initialize_rcv_mss(sk);
@@ -3863,7 +3865,7 @@ static void tcp_connect_init(struct sock *sk) 
	/* limit the window selection if the user enforce a smaller rx buffer */

	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&

	    (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0))

		tp->window_clamp = tcp_full_space(sk);

		WRITE_ONCE(tp->window_clamp, tcp_full_space(sk));



	rcv_wnd = tcp_rwnd_init_bpf(sk);

	if (rcv_wnd == 0)

net/ipv6/syncookies.c

+1 −1
Original line number Diff line number Diff line
@@ -246,7 +246,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) 
		}

	}



	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);

	req->rsk_window_clamp = READ_ONCE(tp->window_clamp) ? :dst_metric(dst, RTAX_WINDOW);

	/* limit the window selection if the user enforce a smaller rx buffer */

	full_space = tcp_full_space(sk);

	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&