staging: vchiq: Fix bulk userdata handling

The addition of the local 'userdata' pointer to
vchiq_irq_queue_bulk_tx_rx omitted the case where neither BLOCKING nor
WAITING modes are used, in which case the value provided by the
caller is not returned to them as expected, but instead it is replaced
with a NULL. This lack of a suitable context may cause the application
to crash or otherwise malfunction.

Fixes: 4184da4f ("staging: vchiq: fix __user annotations")
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Link: https://lore.kernel.org/r/20210105162030.1415213-2-phil@raspberrypi.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c

@@ -958,7 +958,7 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
 	struct vchiq_service *service;
 	struct bulk_waiter_node *waiter = NULL;
 	bool found = false;
-	void *userdata = NULL;
+	void *userdata;
 	int status = 0;
 	int ret;
 
@@ -997,6 +997,8 @@ static int vchiq_irq_queue_bulk_tx_rx(struct vchiq_instance *instance,
 			"found bulk_waiter %pK for pid %d", waiter,
 			current->pid);
 		userdata = &waiter->bulk_waiter;
+	} else {
+		userdata = args->userdata;
 	}
 
 	status = vchiq_bulk_transfer(args->handle, NULL, args->data, args->size,