[RFC PATCH v5 06/17] vsock: fix EPOLLERR set on non-empty error queue

[Arseniy Krasnov]

If socket's error queue is not empty, EPOLLERR must be set. Otherwise,
reader of error queue won't detect data in it using EPOLLERR bit.
Currently for AF_VSOCK this is reproducible only with MSG_ZEROCOPY, as
this feature is the only user of an error queue of the socket.

Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
---
 Changelog:
 v4 -> v5:
  * Change commit message as Fix patch. Also add details that this
    problem could be reproduced only with MSG_ZEROCOPY transmission
    mode.

 net/vmw_vsock/af_vsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index efb8a0937a13..45fd20c4ed50 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1030,7 +1030,7 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
 	poll_wait(file, sk_sleep(sk), wait);
 	mask = 0;
 
-	if (sk->sk_err)
+	if (sk->sk_err || !skb_queue_empty_lockless(&sk->sk_error_queue))
 		/* Signify that there has been an error on this socket. */
 		mask |= EPOLLERR;
 
-- 
2.25.1