4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
[ Upstream commit 45d872f0e65593176d880ec148f41ad7c02e40a7 ]
Once sk->sk_state is changed to TCP_LISTEN, it never changes.
unix_accept() takes advantage of this characteristics; it does not
hold the listener's unix_state_lock() and only acquires recvq lock
to pop one skb.
It means unix_state_lock() does not prevent the queue length from
changing in unix_stream_connect().
Thus, we need to use unix_recvq_full_lockless() to avoid data-race.
Now we remove unix_recvq_full() as no one uses it.
Note that we can remove READ_ONCE() for sk->sk_max_ack_backlog in
unix_recvq_full_lockless() because of the following reasons:
(1) For SOCK_DGRAM, it is a written-once field in unix_create1()
(2) For SOCK_STREAM and SOCK_SEQPACKET, it is changed under the
listener's unix_state_lock() in unix_listen(), and we hold
the lock in unix_stream_connect()
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/unix/af_unix.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 4a4b6d2544534..dfcafbb8cd0e0 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -194,15 +194,9 @@ static inline int unix_may_send(struct sock *sk, struct sock *osk)
return unix_peer(osk) == NULL || unix_our_peer(sk, osk);
}
-static inline int unix_recvq_full(const struct sock *sk)
-{
- return skb_queue_len(&sk->sk_receive_queue) > sk->sk_max_ack_backlog;
-}
-
static inline int unix_recvq_full_lockless(const struct sock *sk)
{
- return skb_queue_len_lockless(&sk->sk_receive_queue) >
- READ_ONCE(sk->sk_max_ack_backlog);
+ return skb_queue_len_lockless(&sk->sk_receive_queue) > sk->sk_max_ack_backlog;
}
struct sock *unix_peer_get(struct sock *s)
@@ -1306,7 +1300,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
if (other->sk_shutdown & RCV_SHUTDOWN)
goto out_unlock;
- if (unix_recvq_full(other)) {
+ if (unix_recvq_full_lockless(other)) {
err = -EAGAIN;
if (!timeo)
goto out_unlock;
--
2.43.0
