[PATCH v2 2/2] vsock: fix possible infinite sleep in vsock_connectible_wait_data()

[Dexuan Cui <decui@microsoft.com>]

Currently vsock_connectible_has_data() may miss a wakeup operation
between vsock_connectible_has_data() == 0 and the prepare_to_wait().

Fix the race by adding the process to the wait queue before checking
vsock_connectible_has_data().

Fixes: b3f7fd54881b ("af_vsock: separate wait data loop")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---

Changes in v2 (Thanks Stefano!):
  Fixed a typo in the commit message.
  Removed the unnecessary finish_wait() at the end of the loop.

 net/vmw_vsock/af_vsock.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index d258fd43092e..884eca7f6743 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1905,8 +1905,11 @@ static int vsock_connectible_wait_data(struct sock *sk,
 	err = 0;
 	transport = vsk->transport;
 
-	while ((data = vsock_connectible_has_data(vsk)) == 0) {
+	while (1) {
 		prepare_to_wait(sk_sleep(sk), wait, TASK_INTERRUPTIBLE);
+		data = vsock_connectible_has_data(vsk);
+		if (data != 0)
+			break;
 
 		if (sk->sk_err != 0 ||
 		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-- 
2.25.1