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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
This commit is contained in:
Eric Dumazet 2019-10-09 15:32:35 -07:00 committed by Jakub Kicinski
parent 8265792bf8
commit eac66402d1
5 changed files with 7 additions and 5 deletions
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4
include/net/sock.h
View File

@ -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.

2
net/core/filter.c
View File

@ -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) {

2
net/core/sock.c
View File

@ -974,7 +974,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
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:

2
net/ipv4/tcp.c
View File

@ -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);

2
net/sched/em_meta.c
View File

@ -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)