From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Grygorii.Strashko@linaro.org" Subject: Re: [PATCH] PM / clock_ops: Fix clock error check in __pm_clk_add() Date: Tue, 12 May 2015 16:55:39 +0300 Message-ID: <5552065B.1020501@linaro.org> References: <1431074863-19124-1-git-send-email-geert+renesas@glider.be> <20150508171955.GA38039@dtor-ws> <20150508210557.GC38039@dtor-ws> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f172.google.com ([209.85.212.172]:36446 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753247AbbELNzk (ORCPT ); Tue, 12 May 2015 09:55:40 -0400 Received: by wizk4 with SMTP id k4so155046931wiz.1 for ; Tue, 12 May 2015 06:55:38 -0700 (PDT) In-Reply-To: <20150508210557.GC38039@dtor-ws> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Dmitry Torokhov , Geert Uytterhoeven Cc: Geert Uytterhoeven , "Rafael J. Wysocki" , Kevin Hilman , Santosh Shilimkar , Linux PM list , "linux-kernel@vger.kernel.org" Hi Dmitry, On 05/09/2015 12:05 AM, Dmitry Torokhov wrote: > On Fri, May 08, 2015 at 10:59:04PM +0200, Geert Uytterhoeven wrote: >> On Fri, May 8, 2015 at 7:19 PM, Dmitry Torokhov >> wrote: >>> On Fri, May 08, 2015 at 10:47:43AM +0200, Geert Uytterhoeven wrote: >>>> In the final iteration of commit 245bd6f6af8a62a2 ("PM / clock_ops: Add >>>> pm_clk_add_clk()"), a refcount increment was added by Grygorii Strashko. >>>> However, the accompanying IS_ERR() check operates on the wrong clock >>>> pointer, which is always zero at this point, i.e. not an error. >>>> This may lead to a NULL pointer dereference later, when __clk_get() >>>> tries to dereference an error pointer. >>>> >>>> Check the passed clock pointer instead to fix this. >>> >>> Frankly I would remove the check altogether. Why do we only check for >>> IS_ERR and not NULL or otherwise validate the pointer? The clk is passed >> >> __clk_get() does the NULL check. > > No, not really. It _handles_ clk being NULL and returns "everything is > fine". In any case it is __clk_get's decision what to do. > > I dislike gratuitous checks of arguments passed in. Instead of relying > on APIs refusing grabage we better not pass garbage to these APIs in the > first place. So I'd change it to trust that we are given a usable > pointer and simply do: > > if (!__clk_get(clk)) { > kfree(ce); > return -ENOENTl > } Not sure this is right thing to do, because this API initially was intended to be used as below [1]: clk = of_clk_get(dev->of_node, i)); ret = pm_clk_add_clk(dev, clk); clk_put(clk); and of_clk_get may return ERR_PTR(). So, personally I prefer initial fix from Geert. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/296586.html -- regards, -grygorii