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 29562C433FE for ; Thu, 31 Mar 2022 11:38:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235243AbiCaLj6 (ORCPT ); Thu, 31 Mar 2022 07:39:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232097AbiCaLjz (ORCPT ); Thu, 31 Mar 2022 07:39:55 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E52B0208247; Thu, 31 Mar 2022 04:38:07 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 8015961534; Thu, 31 Mar 2022 11:38:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A86DC340ED; Thu, 31 Mar 2022 11:38:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1648726686; bh=/jI8Y2KnjFMiq0vz5kPkp3upN5zf40lZ63WmlzK4JIg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QmbXyl3x9opWS5I5HuQOfmYLg/S2gTYFf+btlwjkEb6OYK9x2eOjky/1VGHzeV3Yg 5Mht1VcgA+iUjho9ZlpOTynkhLoXqf2kWZAGWR1VZkMW4XqbdC9P5yRYlodsLrzAye +yGquo1sdj/0AF0xWrDn/7acj7s1L23ljSAYStSM= Date: Thu, 31 Mar 2022 13:38:02 +0200 From: Greg KH To: Heikki Krogerus Cc: Won Chung , Tomas Winkler , Mika Westerberg , Benson Leung , Prashant Malani , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v3] misc/mei: Add NULL check to component match callback functions Message-ID: References: <20220331084918.2592699-1-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: linux-kernel@vger.kernel.org On Thu, Mar 31, 2022 at 12:32:24PM +0300, Heikki Krogerus wrote: > On Thu, Mar 31, 2022 at 11:00:46AM +0200, Greg KH wrote: > > On Thu, Mar 31, 2022 at 08:49:18AM +0000, Won Chung wrote: > > > Component match callback functions need to check if expected data is > > > passed to them. Without this check, it can cause a NULL pointer > > > dereference when another driver registers a component before i915 > > > drivers have their component master fully bind. > > > > How can that happen in a real system? Or does this just happen for when > > you are doing development and testing? > > > > > > > > Fixes: 1e8d19d9b0dfc ("mei: hdcp: bind only with i915 on the same PCH") > > > Fixes: c2004ce99ed73 ("mei: pxp: export pavp client to me client bus") > > > Suggested-by: Heikki Krogerus > > > Suggested-by: Mika Westerberg > > > Signed-off-by: Won Chung > > > Cc: stable@vger.kernel.org > > > > Why does this need to go to stable? How can this be triggered in older > > kernels? > > > > > --- > > > Changes from v2: > > > - Correctly add "Suggested-by" tag > > > - Add "Cc: stable@vger.kernel.org" > > > > > > Changes from v1: > > > - Add "Fixes" tag > > > - Send to stable@vger.kernel.org > > > > > > drivers/misc/mei/hdcp/mei_hdcp.c | 2 +- > > > drivers/misc/mei/pxp/mei_pxp.c | 2 +- > > > 2 files changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c > > > index ec2a4fce8581..843dbc2b21b1 100644 > > > --- a/drivers/misc/mei/hdcp/mei_hdcp.c > > > +++ b/drivers/misc/mei/hdcp/mei_hdcp.c > > > @@ -784,7 +784,7 @@ static int mei_hdcp_component_match(struct device *dev, int subcomponent, > > > { > > > struct device *base = data; > > > > > > - if (strcmp(dev->driver->name, "i915") || > > > + if (!base || !dev->driver || strcmp(dev->driver->name, "i915") || > > > > How can base be NULL? > > > > > > > subcomponent != I915_COMPONENT_HDCP) > > > return 0; > > > > > > diff --git a/drivers/misc/mei/pxp/mei_pxp.c b/drivers/misc/mei/pxp/mei_pxp.c > > > index f7380d387bab..e32a81da8af6 100644 > > > --- a/drivers/misc/mei/pxp/mei_pxp.c > > > +++ b/drivers/misc/mei/pxp/mei_pxp.c > > > @@ -131,7 +131,7 @@ static int mei_pxp_component_match(struct device *dev, int subcomponent, > > > { > > > struct device *base = data; > > > > > > - if (strcmp(dev->driver->name, "i915") || > > > + if (!base || !dev->driver || strcmp(dev->driver->name, "i915") || > > > > Same here, shouldn't this be caught by the driver core or bus and match > > should not be called? > > > > Why not fix this in the component/driver core instead? > > A component is just a device that is declared to be a "component", and > the code that declares it as component does not have to be the driver > of that device. You simply can't assume that it's bind to a driver > like this function does. > > In our case the "components" are USB ports, so devices that are never > bind to drivers. And going off of the driver name is sane? That feels ripe for bugs and problems in the future, but hey, I don't understand the need for this driver to care about another driver at all. And why is a USB device being passed to something that it thinks is a PCI device? That too feels really wrong and ripe for problems. thanks, greg k-h