nfc: virtual_ncidev: Add variable to check if ndev is running

syzbot reported an memory leak that happens when an skb is add to
send_buff after virtual nci closed.
This patch adds a variable to track if the ndev is running before
handling new skb in send function.

Signed-off-by: Nguyen Dinh Phi <phind.uet@gmail.com>
Reported-by: syzbot+6eb09d75211863f15e3e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/00000000000075472b06007df4fb@google.com
Reviewed-by: Bongsu Jeon
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: ita93

drivers/nfc/virtual_ncidev.c

@@ -26,10 +26,14 @@ struct virtual_nci_dev {
 	struct mutex mtx;
 	struct sk_buff *send_buff;
 	struct wait_queue_head wq;
+	bool running;
 };
 
 static int virtual_nci_open(struct nci_dev *ndev)
 {
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	vdev->running = true;
 	return 0;
 }
 
@@ -40,6 +44,7 @@ static int virtual_nci_close(struct nci_dev *ndev)
 	mutex_lock(&vdev->mtx);
 	kfree_skb(vdev->send_buff);
 	vdev->send_buff = NULL;
+	vdev->running = false;
 	mutex_unlock(&vdev->mtx);
 
 	return 0;
@@ -50,7 +55,7 @@ static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
 	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
 
 	mutex_lock(&vdev->mtx);
-	if (vdev->send_buff) {
+	if (vdev->send_buff || !vdev->running) {
 		mutex_unlock(&vdev->mtx);
 		kfree_skb(skb);
 		return -1;