From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752482AbeDKGQg (ORCPT ); Wed, 11 Apr 2018 02:16:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:43142 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751815AbeDKGQf (ORCPT ); Wed, 11 Apr 2018 02:16:35 -0400 Date: Wed, 11 Apr 2018 08:16:33 +0200 Message-ID: From: Takashi Iwai To: Ram Pai Cc: Andrew Morton , Bjorn Helgaas , Michael Henders , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] resource: Fix integer overflow at reallocation In-Reply-To: <20180411003744.GC15890@ram.oc3035372033.ibm.com> References: <20180408072026.27365-1-tiwai@suse.de> <20180409172326.944143fd13db2601e4dee9b0@linux-foundation.org> <20180410134239.483fe34525db647f2f3d1ece@linux-foundation.org> <20180411003744.GC15890@ram.oc3035372033.ibm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") 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 Wed, 11 Apr 2018 02:37:44 +0200, Ram Pai wrote: > > On Tue, Apr 10, 2018 at 01:42:39PM -0700, Andrew Morton wrote: > > On Tue, 10 Apr 2018 06:54:11 +0200 Takashi Iwai wrote: > > > > > On Tue, 10 Apr 2018 02:23:26 +0200, > > > Andrew Morton wrote: > > > > > > > > On Sun, 8 Apr 2018 09:20:26 +0200 Takashi Iwai wrote: > > > > > > > > > We've got a bug report indicating a kernel panic at booting on an > > > > > x86-32 system, and it turned out to be the invalid resource assigned > > > > > after PCI resource reallocation. __find_resource() first aligns the > > > > > resource start address and resets the end address with start+size-1 > > > > > accordingly, then checks whether it's contained. Here the end address > > > > > may overflow the integer, although resource_contains() still returns > > > > > true because the function validates only start and end address. So > > > > > this ends up with returning an invalid resource (start > end). > > > > > > > > > > There was already an attempt to cover such a problem in the commit > > > > > 47ea91b4052d ("Resource: fix wrong resource window calculation"), but > > > > > this case is an overseen one. > > > > > > > > > > This patch adds the validity check in resource_contains() to see > > > > > whether the given resource has a valid range for avoiding the integer > > > > > overflow problem. > > > > > > > > > > ... > > > > > > > > > > --- a/include/linux/ioport.h > > > > > +++ b/include/linux/ioport.h > > > > > @@ -212,6 +212,9 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2) > > > > > return false; > > > > > if (r1->flags & IORESOURCE_UNSET || r2->flags & IORESOURCE_UNSET) > > > > > return false; > > > > > + /* sanity check whether it's a valid resource range */ > > > > > + if (r2->end < r2->start) > > > > > + return false; > > > > > return r1->start <= r2->start && r1->end >= r2->end; > > > > > } > > > > > > > > This doesn't look like the correct place to handle this? Clearly .end > > > > < .start is an invalid state for a resource and we should never have > > > > constructed such a thing in the first place? So adding a check at the > > > > place where this resource was initially created seems to be the correct > > > > fix? > > > > > > Yes, that was also my first thought and actually the v1 patch was like > > > that. > > > > Yes, I do prefer. > > > > > The v2 one was by Ram's suggestion so that we can cover > > > potential bugs by all other callers as well. > > > > That could be done as a separate thing? > > the first approach will fix overflows in just that particular case. The > second approach will catch and error-out overflows anywhere. There is a > short-term down side to the second approach; it might cause a slew of > error reports but will eventually help clean up all bad behavior. For that purpose, maybe we should do in two folds: at first fix this specific issue in __find_resource(), then put the sanity check in resource_contains() in addition but with WARN_ON() so that we can catch more obviously. thanks, Takashi