[PATCH 4.13 24/53] ALSA: line6: Fix NULL dereference at podhd_disconnect()

[Greg Kroah-Hartman]

4.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@xxxxxxx>

commit 54a4b2b45817ea2365b40c923c098a26af0c0dbb upstream.

When podhd_init() failed with the acquiring a ctrl i/f, the line6
helper still calls the disconnect callback that eventually calls again
usb_driver_release_interface() with the NULL intf.

Put the proper NULL check before calling it for avoiding an Oops.

Fixes: fc90172ba283 ("ALSA: line6: Claim pod x3 usb data interface")
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 sound/usb/line6/podhd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/sound/usb/line6/podhd.c
+++ b/sound/usb/line6/podhd.c
@@ -301,7 +301,8 @@ static void podhd_disconnect(struct usb_
 
 		intf = usb_ifnum_to_if(line6->usbdev,
 					pod->line6.properties->ctrl_if);
-		usb_driver_release_interface(&podhd_driver, intf);
+		if (intf)
+			usb_driver_release_interface(&podhd_driver, intf);
 	}
 }