From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A284C433B4 for ; Mon, 26 Apr 2021 16:55:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4E3461165 for ; Mon, 26 Apr 2021 16:55:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234840AbhDZQ4U (ORCPT ); Mon, 26 Apr 2021 12:56:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:60208 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233736AbhDZQ4T (ORCPT ); Mon, 26 Apr 2021 12:56:19 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id F065961076; Mon, 26 Apr 2021 16:55:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619456137; bh=K8s2HR2UdDqXVvoQjGH6zirtLDDVxviKtltWnei6bNk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wr5110SEyhbwJHa7bvzB/A1tCbCapnx8RlAEka1r87GwMue32H9kwBpLhLD1003IC W6lES/hT8xQhZ7OAR4kkTgZ76bjf2zuwXOhhxXXHyQFmtQqHUoe0+dTx4K0g0Jo4fw Grmdi15dN8Zu8v32uhbb/TllmUDzVfTVyKviTVM0= Date: Mon, 26 Apr 2021 18:55:34 +0200 From: Greg Kroah-Hartman To: Kees Cook Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Aditya Pakki , kjlu@umn.edu, Borislav Petkov , "H. Peter Anvin" , Joe Perches , Nicolai Stange , Roland Dreier Subject: Re: [PATCH 113/190] Revert "x86/hpet: Prevent potential NULL pointer dereference" Message-ID: References: <20210421130105.1226686-1-gregkh@linuxfoundation.org> <20210421130105.1226686-114-gregkh@linuxfoundation.org> <202104211245.F5FEC8D15D@keescook> <87im4dx5cc.ffs@nanos.tec.linutronix.de> <202104230201.EEB997CD8@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202104230201.EEB997CD8@keescook> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 23, 2021 at 02:03:50AM -0700, Kees Cook wrote: > On Fri, Apr 23, 2021 at 01:33:07AM +0200, Thomas Gleixner wrote: > > On Wed, Apr 21 2021 at 12:49, Kees Cook wrote: > > > On Wed, Apr 21, 2021 at 02:59:48PM +0200, Greg Kroah-Hartman wrote: > > >> diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c > > >> index 08651a4e6aa0..0515a97bf6f5 100644 > > >> --- a/arch/x86/kernel/hpet.c > > >> +++ b/arch/x86/kernel/hpet.c > > >> @@ -930,8 +930,6 @@ int __init hpet_enable(void) > > >> return 0; > > >> > > >> hpet_set_mapping(); > > >> - if (!hpet_virt_address) > > >> - return 0; > > >> > > >> /* Validate that the config register is working */ > > >> if (!hpet_cfg_working()) > > > > > > FWIW, this patch looks harmless. It is checking for a failure in > > > hpet_set_mapping(), and avoids the following code from performing > > > 0-offset reads. hpet_set_mapping() is likely to never fail in real-world > > > situations. *shrug* > > > > 'likely never to fail' is clearly a receipe for disaster and you should > > know that. > > Of course -- I prefer to keep the sanity check. It just wasn't as good > as it could have been: it's not clear just by looking at the patch how > hpet_virt_address and hpet_set_mapping() are related. > > > > > > I think it would make more sense for the check to live in > > > hpet_cfg_working(), though. > > > > No. That does not make any sense at all. > > > > The proper change would have been to make hpet_set_mapping() return > > an error/success code and act on that. > > > > But that does _NOT_ make the patch invalid. > > > > I'm pretty sure that I looked at it and thought about the proper > > solution (see above) and then shrugged it off because of overload... > > Right, no, I was saying the original patch should stay. It shouldn't be > reverted. > > Greg, please drop this patch from the revert list. Now dropped, thanks for the review. greg k-h