Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932864AbbELQnE (ORCPT ); Tue, 12 May 2015 12:43:04 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:33146 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751583AbbELQnA (ORCPT ); Tue, 12 May 2015 12:43:00 -0400 Date: Tue, 12 May 2015 09:42:54 -0700 From: Dmitry Torokhov To: "Grygorii.Strashko@linaro.org" Cc: Geert Uytterhoeven , Geert Uytterhoeven , "Rafael J. Wysocki" , Kevin Hilman , Santosh Shilimkar , Linux PM list , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] PM / clock_ops: Fix clock error check in __pm_clk_add() Message-ID: <20150512164254.GA20725@dtor-ws> References: <1431074863-19124-1-git-send-email-geert+renesas@glider.be> <20150508171955.GA38039@dtor-ws> <20150508210557.GC38039@dtor-ws> <5552065B.1020501@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5552065B.1020501@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2666 Lines: 71 On Tue, May 12, 2015 at 04:55:39PM +0300, Grygorii.Strashko@linaro.org wrote: > 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(). Jeez, that sequence was not meant to be taken literally, it does miss error handling completely. If you notice the majority of users of this API do something like below: i = 0; while ((clk = of_clk_get(dev->of_node, i++)) && !IS_ERR(clk)) { dev_dbg(dev, "adding clock '%s' to list of PM clocks\n", __clk_get_name(clk)); error = pm_clk_add_clk(dev, clk); clk_put(clk); if (error) { dev_err(dev, "pm_clk_add_clk failed %d\n", error); pm_clk_destroy(dev); return error; } } i.e. it already validates clk pointer before passing it on since it needs to know when to stop iterating. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/