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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 736C5C433EF for ; Thu, 31 Mar 2022 12:56:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231592AbiCaM6h (ORCPT ); Thu, 31 Mar 2022 08:58:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234217AbiCaM6f (ORCPT ); Thu, 31 Mar 2022 08:58:35 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A69432128D9; Thu, 31 Mar 2022 05:56:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 8AA23CE21CA; Thu, 31 Mar 2022 12:56:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B5FFC340F2; Thu, 31 Mar 2022 12:56:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1648731404; bh=IJMv8QRbmsZe6PkwmtIOo18HaNy2h/hxvfgNjsECIdM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pxX4SEJLNXuMz+TwGcWZxflUuhMTVMnz2lbN5MlgXp/LT4OgVjKg/U205ilgAcW0J qsH34tY1EjGKDg0iMUstTI4Xg2P07WxraC9s7VFRQZBtsxbpke83WsPNArI45RRXak JPPjFQVYIU60zciozYRj2SmBRRpO1Lk2xDWNlIPM= Date: Thu, 31 Mar 2022 14:56:41 +0200 From: Greg KH To: Heikki Krogerus Cc: Takashi Iwai , Won Chung , Jaroslav Kysela , Takashi Iwai , Mika Westerberg , Benson Leung , Prashant Malani , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] sound/hda: Add NULL check to component match callback function Message-ID: References: <20220330211913.2068108-1-wonchung@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Mar 31, 2022 at 03:52:14PM +0300, Heikki Krogerus wrote: > Hi Greg, > > On Thu, Mar 31, 2022 at 01:39:51PM +0200, Greg KH wrote: > > On Thu, Mar 31, 2022 at 12:25:43PM +0300, Heikki Krogerus wrote: > > > On Thu, Mar 31, 2022 at 11:12:55AM +0200, Takashi Iwai wrote: > > > > > > > - if (!strcmp(dev->driver->name, "i915") && > > > > > > > + if (dev->driver && !strcmp(dev->driver->name, "i915") && > > > > > > > > > > > > Can NULL dev->driver be really seen? I thought the components are > > > > > > added by the drivers, hence they ought to have the driver field set. > > > > > > But there can be corner cases I overlooked. > > > > > > > > > > > > > > > > > > thanks, > > > > > > > > > > > > Takashi > > > > > > > > > > Hi Takashi, > > > > > > > > > > When I try using component_add in a different driver (usb4 in my > > > > > case), I think dev->driver here is NULL because the i915 drivers do > > > > > not have their component master fully bound when this new component is > > > > > registered. When I test it, it seems to be causing a crash. > > > > > > > > Hm, from where component_add*() is called? Basically dev->driver must > > > > be already set before the corresponding driver gets bound at > > > > __driver_probe_deviec(). So, if the device is added to component from > > > > the corresponding driver's probe, dev->driver must be non-NULL. > > > > > > The code that declares a device as component does not have to be the > > > driver of that device. > > > > > > In our case the components are USB ports, and they are devices that > > > are actually never bind to any drivers: drivers/usb/core/port.c > > > > Why is a USB device being passed to this code that assumes it is looking > > for a PCI device with a specific driver name? As I mentioned on the > > mei patch, triggering off of a name is really a bad idea, as is assuming > > the device type without any assurance it is such a device (there's a > > reason we didn't provide device type identification in the driver core, > > don't abuse that please...) > > I totally agree. This driver is making a whole bunch of assumptions > when it should not make any assumptions. And yes, one of those > assumptions is that the driver of the device has a specific name, and > that is totally crazy. So why is it making those assumptions? I have > no idea, but is does, and they are now causing the first problem - > NULL pointer dereference. > > This patch (and that other) is only proposing a simple way to solve > that NULL pointer dereference issue by adding some sanity checks. If > that's no OK, and the whole driver should be refactored instead, then > that is perfectly OK by me, but that has to be done by somebody who > understands what exactly is the driver and the device it's controlling > doing (and for). This all needs to be refactored to not do this at all. thanks, greg k-h