From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752395AbdEDKQV (ORCPT ); Thu, 4 May 2017 06:16:21 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:38180 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751452AbdEDKQN (ORCPT ); Thu, 4 May 2017 06:16:13 -0400 Date: Thu, 4 May 2017 12:16:08 +0200 From: Daniel Lezcano To: "Li, Fei" Cc: Andy Shevchenko , "Shi, FengX" , "rjw@rjwysocki.net" , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Koul, Vinod" Subject: Re: [PATCH V3] cpuidle: check dev before usage in cpuidle_use_deepest_state Message-ID: <20170504101608.GA5252@mai> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 04, 2017 at 09:00:52AM +0000, Li, Fei wrote: > In case of there is no cpuidle devices registered, dev will be null, and > panic will be triggered like below; > In this patch, add checking of dev before usage, like that done in > cpuidle_idle_call. > > Panic without fix: > [ 184.961328] BUG: unable to handle kernel NULL pointer dereference at > (null) > [ 184.961328] IP: cpuidle_use_deepest_state+0x30/0x60 > ... > [ 184.961328] play_idle+0x8d/0x210 > [ 184.961328] ? __schedule+0x359/0x8e0 > [ 184.961328] ? _raw_spin_unlock_irqrestore+0x28/0x50 > [ 184.961328] ? kthread_queue_delayed_work+0x41/0x80 > [ 184.961328] clamp_idle_injection_func+0x64/0x1e0 > > Fixes: bb8313b603eb8 ("cpuidle: Allow enforcing deepest idle state selection") > Signed-off-by: Li, Fei > Tested-by: Shi, Feng > Reviewed-by: Andy Shevchenko > Reviewed-by: Koul, Vinod > --- > drivers/cpuidle/cpuidle.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 548b90b..2706be7 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enable) > > preempt_disable(); > dev = cpuidle_get_device(); > - dev->use_deepest_state = enable; > + if (dev) > + dev->use_deepest_state = enable; This change is acceptable as a hot fix but the question is 'why is this function called if there is no cpuidle driver registered?' > preempt_enable(); > } > > -- > 1.9.1 > > Best Regards, > Fei -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog