From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752584AbeDJUml (ORCPT ); Tue, 10 Apr 2018 16:42:41 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38196 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751799AbeDJUmk (ORCPT ); Tue, 10 Apr 2018 16:42:40 -0400 Date: Tue, 10 Apr 2018 13:42:39 -0700 From: Andrew Morton To: Takashi Iwai Cc: Ram Pai , Bjorn Helgaas , Michael Henders , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] resource: Fix integer overflow at reallocation Message-Id: <20180410134239.483fe34525db647f2f3d1ece@linux-foundation.org> In-Reply-To: References: <20180408072026.27365-1-tiwai@suse.de> <20180409172326.944143fd13db2601e4dee9b0@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?