From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932428AbcHVRnz (ORCPT ); Mon, 22 Aug 2016 13:43:55 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:35794 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755868AbcHVRnw (ORCPT ); Mon, 22 Aug 2016 13:43:52 -0400 Date: Mon, 22 Aug 2016 13:43:30 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Jiri Slaby cc: Vittorio Zecca , , USB list , Linux kernel mailing list Subject: Re: UBSAN: Undefined behaviour in linux-4.7.2/drivers/usb/core/devio.c:1713:25 In-Reply-To: <48b3a1b9-e6c1-bea0-bb10-488818f7812d@suse.cz> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 21 Aug 2016, Jiri Slaby wrote: > Cc: proper lists. > > ep->desc.bInterval seems to be 0 here. > > On 08/21/2016, 12:42 PM, Vittorio Zecca wrote: > > I am not sure this is the right place so please bear with me... > > From Vittorio Zecca > > > > After compiling kernel 4.7.2 with ubsan I got the following messages > > at boot time: > > > > (devio.c:1713 is "as->urb->interval = 1 << min(15, ep->desc.bInterval - 1);") > > > > [ +0.354486] ================================================================================ > > [ +0.000008] UBSAN: Undefined behaviour in > > /home/vitti/1tb/vitti/rpmbuild/SOURCES/linux-4.7.2/drivers/usb/core/devio.c:1713:25 > > [ +0.000004] shift exponent -1 is negative As far as I can see, this isn't possible. The usb_parse_endpoint() routine in drivers/usb/core/config.c is supposed to guarantee that ep->desc.bInterval is never 0. More information from Vittorio would be helpful. For example, what shows up in /sys/kernel/debug/usb/devices (after mounting a debugfs filesystem on /sys/kernel/debug)? Alan Stern