usb: raw-gadget: fix raw_event_queue_fetch locking

If queue->size check in raw_event_queue_fetch() fails (which normally
shouldn't happen, that check is a fail-safe), the function returns
without reenabling interrupts. This patch fixes that issue, along with
propagating the cause of failure to the function caller.

Fixes: f2c2e717 ("usb: gadget: add raw-gadget interface")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/9f7ce7a1472cfb9447f6c5a494186fa1f2670f6f.1586270396.git.andreyknvl@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/legacy/raw_gadget.c

@@ -81,6 +81,7 @@ static int raw_event_queue_add(struct raw_event_queue *queue,
 static struct usb_raw_event *raw_event_queue_fetch(
 				struct raw_event_queue *queue)
 {
+	int ret;
 	unsigned long flags;
 	struct usb_raw_event *event;
 
@@ -89,11 +90,18 @@ static struct usb_raw_event *raw_event_queue_fetch(
 	 * there's at least one event queued by decrementing the semaphore,
 	 * and then take the lock to protect queue struct fields.
 	 */
-	if (down_interruptible(&queue->sema))
-		return NULL;
+	ret = down_interruptible(&queue->sema);
+	if (ret)
+		return ERR_PTR(ret);
 	spin_lock_irqsave(&queue->lock, flags);
-	if (WARN_ON(!queue->size))
-		return NULL;
+	/*
+	 * queue->size must have the same value as queue->sema counter (before
+	 * the down_interruptible() call above), so this check is a fail-safe.
+	 */
+	if (WARN_ON(!queue->size)) {
+		spin_unlock_irqrestore(&queue->lock, flags);
+		return ERR_PTR(-ENODEV);
+	}
 	event = queue->events[0];
 	queue->size--;
 	memmove(&queue->events[0], &queue->events[1],
@@ -522,10 +530,17 @@ static int raw_ioctl_event_fetch(struct raw_dev *dev, unsigned long value)
 	spin_unlock_irqrestore(&dev->lock, flags);
 
 	event = raw_event_queue_fetch(&dev->queue);
-	if (!event) {
+	if (PTR_ERR(event) == -EINTR) {
 		dev_dbg(&dev->gadget->dev, "event fetching interrupted\n");
 		return -EINTR;
 	}
+	if (IS_ERR(event)) {
+		dev_err(&dev->gadget->dev, "failed to fetch event\n");
+		spin_lock_irqsave(&dev->lock, flags);
+		dev->state = STATE_DEV_FAILED;
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return -ENODEV;
+	}
 	length = min(arg.length, event->length);
 	if (copy_to_user((void __user *)value, event, sizeof(*event) + length))
 		return -EFAULT;