Commit eac66402 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: annotate sk->sk_rcvlowat lockless reads 



sock_rcvlowat() or int_sk_rcvlowat() might be called without the socket
lock for example from tcp_poll().

Use READ_ONCE() to document the fact that other cpus might change
sk->sk_rcvlowat under us and avoid KCSAN splats.

Use WRITE_ONCE() on write sides too.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
parent 8265792b

include/net/sock.h

+3 −1
Original line number Diff line number Diff line
@@ -2271,7 +2271,9 @@ static inline long sock_sndtimeo(const struct sock *sk, bool noblock) 


static inline int sock_rcvlowat(const struct sock *sk, int waitall, int len)

{

	return (waitall ? len : min_t(int, sk->sk_rcvlowat, len)) ? : 1;

	int v = waitall ? len : min_t(int, READ_ONCE(sk->sk_rcvlowat), len);



	return v ?: 1;

}



/* Alas, with timeout socket operations are not restartable.

net/core/filter.c

+1 −1
Original line number Diff line number Diff line
@@ -4274,7 +4274,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, 
		case SO_RCVLOWAT:

			if (val < 0)

				val = INT_MAX;

			sk->sk_rcvlowat = val ? : 1;

			WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);

			break;

		case SO_MARK:

			if (sk->sk_mark != val) {

net/core/sock.c

+1 −1
Original line number Diff line number Diff line
@@ -974,7 +974,7 @@ set_rcvbuf: 
		if (sock->ops->set_rcvlowat)

			ret = sock->ops->set_rcvlowat(sk, val);

		else

			sk->sk_rcvlowat = val ? : 1;

			WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);

		break;



	case SO_RCVTIMEO_OLD:

net/ipv4/tcp.c

+1 −1
Original line number Diff line number Diff line
@@ -1699,7 +1699,7 @@ int tcp_set_rcvlowat(struct sock *sk, int val) 
	else

		cap = sock_net(sk)->ipv4.sysctl_tcp_rmem[2] >> 1;

	val = min(val, cap);

	sk->sk_rcvlowat = val ? : 1;

	WRITE_ONCE(sk->sk_rcvlowat, val ? : 1);



	/* Check if we need to signal EPOLLIN right now */

	tcp_data_ready(sk);

net/sched/em_meta.c

+1 −1
Original line number Diff line number Diff line
@@ -554,7 +554,7 @@ META_COLLECTOR(int_sk_rcvlowat) 
		*err = -1;

		return;

	}

	dst->value = sk->sk_rcvlowat;

	dst->value = READ_ONCE(sk->sk_rcvlowat);

}



META_COLLECTOR(int_sk_rcvtimeo)

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