From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752539AbcC2NL1 (ORCPT ); Tue, 29 Mar 2016 09:11:27 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:61448 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751539AbcC2NLY (ORCPT ); Tue, 29 Mar 2016 09:11:24 -0400 From: "Rafael J. Wysocki" To: Darren Hart Cc: Colin King , Sujith Thomas , platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] intel_menlow: set cdev after null device check to avoid null pointer dereference Date: Tue, 29 Mar 2016 15:13:43 +0200 Message-ID: <4083784.LDUSFcvSJY@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.5.0-rc1+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20160328181805.GC26086@dvhart-mobl5.amr.corp.intel.com> References: <1459181919-13825-1-git-send-email-colin.king@canonical.com> <20160328181805.GC26086@dvhart-mobl5.amr.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, March 28, 2016 11:18:05 AM Darren Hart wrote: > On Mon, Mar 28, 2016 at 05:18:39PM +0100, Colin King wrote: > > From: Colin Ian King > > > > intel_menlow_memory_remove sanity checks to see if device is null, however, > > this check is performed after we have already passed device into a call > > to acpi_driver_data. If device is null, then acpi_driver_data will produce > > a null pointer dereference on device. The correct action is to sanity check > > device, then assign cdev, then check if cdev is null. > > > > Hrm, looking at this locally, that all makes sense. > > Taking a step back however, I notice that intel_menlow_memory_remove is an ops > function pointer inside the acpi_driver structure itself, which is called from > acpi_device_remove() (and probe) (drivers/acpi/bus.c). This already verifies > acpi_driver is not NULL and can't get acpi_driver if acpi_device is NULL. So > unless there is some other use case for this callback I'm unaware of (certainly > possible) it appears to be totally redundant to do this checking here. > > +Rafael - is there a best practices for these acpi callbacks with respect to > input validation? No best practices I'm aware of, but if the core does this checks anyway before calling this, they are clearly not necessary here. Thanks, Rafael