[PATCH 2/3] HID: huawei: fix missing hid_is_usb() check

[Jann Horn <jannh@google.com>]

to_usb_interface() can only be used on a hid_device whose parent is really
USB; uhid can create devices that identify as being on BUS_USB, but don't
actually have a USB parent.
Fix the use of to_usb_interface() without a hid_is_usb() check.

I have verified that it is currently possible to trigger a kernel splat due
to this bug in an ASAN build, and that this commit fixes the issue.

Fixes: e93faaca84b7 ("HID: huawei: fix CD30 keyboard report descriptor issue")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
---
 drivers/hid/hid-huawei.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-huawei.c b/drivers/hid/hid-huawei.c
index 6a616bf21b38..ee3fc6f68475 100644
--- a/drivers/hid/hid-huawei.c
+++ b/drivers/hid/hid-huawei.c
@@ -44,11 +44,12 @@ static const __u8 huawei_cd30_kbd_rdesc_fixed[] = {
 static const __u8 *huawei_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 				  unsigned int *rsize)
 {
-	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+	struct usb_interface *intf = hid_is_usb(hdev) ?
+			to_usb_interface(hdev->dev.parent) : NULL;
 
 	switch (hdev->product) {
 	case USB_DEVICE_ID_HUAWEI_CD30KBD:
-		if (intf->cur_altsetting->desc.bInterfaceNumber == 1) {
+		if (!intf || intf->cur_altsetting->desc.bInterfaceNumber == 1) {
 			if (*rsize != sizeof(huawei_cd30_kbd_rdesc_fixed) ||
 				memcmp(huawei_cd30_kbd_rdesc_fixed, rdesc,
 					sizeof(huawei_cd30_kbd_rdesc_fixed)) != 0) {

-- 
2.55.0.rc0.799.gd6f94ed593-goog