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tcp: annotate tp->urg_seq lockless reads 

There two places where we fetch tp->urg_seq while
this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make
sure write side use corresponding WRITE_ONCE() to avoid
store-tearing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-10-10 20:17:43 -07:00 committed by David S. Miller
parent e0d694d638
commit d9b55bf7b6
2 changed files with 4 additions and 3 deletions
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5
net/ipv4/tcp.c
View File

@ -546,7 +546,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
(state != TCP_SYN_RECV || rcu_access_pointer(tp->fastopen_rsk))) {
int target = sock_rcvlowat(sk, 0, INT_MAX);
if (tp->urg_seq == READ_ONCE(tp->copied_seq) &&
if (READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq) &&
!sock_flag(sk, SOCK_URGINLINE) &&
tp->urg_data)
target++;
@ -607,7 +607,8 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
unlock_sock_fast(sk, slow);
break;
case SIOCATMARK:
answ = tp->urg_data && tp->urg_seq == READ_ONCE(tp->copied_seq);
answ = tp->urg_data &&
READ_ONCE(tp->urg_seq) == READ_ONCE(tp->copied_seq);
break;
case SIOCOUTQ:
if (sk->sk_state == TCP_LISTEN)

2
net/ipv4/tcp_input.c
View File

@ -5356,7 +5356,7 @@ static void tcp_check_urg(struct sock *sk, const struct tcphdr *th)
}
tp->urg_data = TCP_URG_NOTYET;
tp->urg_seq = ptr;
WRITE_ONCE(tp->urg_seq, ptr);
/* Disable header prediction. */
tp->pred_flags = 0;