staging: rtl8712: handle firmware load failure

when firmware fails to load we should not call unregister_netdev()
this patch fixes a race condition between rtl871x_load_fw_cb() and
r871xu_dev_remove() and fixes the bug reported by syzbot

Reported-by: syzbot+80899a8a8efe8968cde7@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=80899a8a8efe8968cde7Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200716151324.1036204-1-rkovhaev@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/hal_init.c

@@ -33,7 +33,6 @@ static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 {
 	struct _adapter *adapter = context;
 
-	complete(&adapter->rtl8712_fw_ready);
 	if (!firmware) {
 		struct usb_device *udev = adapter->dvobjpriv.pusbdev;
 		struct usb_interface *usb_intf = adapter->pusb_intf;
@@ -41,11 +40,13 @@ static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 		dev_err(&udev->dev, "r8712u: Firmware request failed\n");
 		usb_put_dev(udev);
 		usb_set_intfdata(usb_intf, NULL);
+		complete(&adapter->rtl8712_fw_ready);
 		return;
 	}
 	adapter->fw = firmware;
 	/* firmware available - start netdev */
 	register_netdev(adapter->pnetdev);
+	complete(&adapter->rtl8712_fw_ready);
 }
 
 static const char firmware_file[] = "rtlwifi/rtl8712u.bin";

drivers/staging/rtl8712/usb_intf.c

@@ -595,12 +595,16 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 	if (pnetdev) {
 		struct _adapter *padapter = netdev_priv(pnetdev);
 
-		usb_set_intfdata(pusb_intf, NULL);
-		release_firmware(padapter->fw);
 		/* never exit with a firmware callback pending */
 		wait_for_completion(&padapter->rtl8712_fw_ready);
+		pnetdev = usb_get_intfdata(pusb_intf);
+		usb_set_intfdata(pusb_intf, NULL);
+		if (!pnetdev)
+			goto firmware_load_fail;
+		release_firmware(padapter->fw);
 		if (drvpriv.drv_registered)
 			padapter->surprise_removed = true;
+		if (pnetdev->reg_state != NETREG_UNINITIALIZED)
 			unregister_netdev(pnetdev); /* will call netdev_close() */
 		flush_scheduled_work();
 		udelay(1);
@@ -614,6 +618,7 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 		 */
 		usb_put_dev(udev);
 	}
+firmware_load_fail:
 	/* If we didn't unplug usb dongle and remove/insert module, driver
 	 * fails on sitesurvey for the first time when device is up.
 	 * Reset usb port for sitesurvey fail issue.