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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86DE4C04EB8 for ; Tue, 4 Dec 2018 14:25:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 54A3A206B7 for ; Tue, 4 Dec 2018 14:25:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 54A3A206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hofr.at Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726741AbeLDOZp (ORCPT ); Tue, 4 Dec 2018 09:25:45 -0500 Received: from 178.115.242.59.static.drei.at ([178.115.242.59]:37927 "EHLO mail.osadl.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725956AbeLDOZo (ORCPT ); Tue, 4 Dec 2018 09:25:44 -0500 Received: by mail.osadl.at (Postfix, from userid 1001) id BD8F85C0FF8; Tue, 4 Dec 2018 14:25:04 +0000 (UTC) Date: Tue, 4 Dec 2018 15:25:04 +0100 From: Nicholas Mc Guire To: Peter Rosin Cc: Nicholas Mc Guire , Wolfram Sang , "linux-i2c@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] i2c: mux: demux-pinctrl: handle failure case of devm_kstrdup() Message-ID: <20181204142504.GA16001@osadl.at> References: <1543658470-20887-1-git-send-email-hofrat@osadl.org> <549eba3a-28b9-e4b0-f680-8fb51b160879@axentia.se> <20181204121318.GB28201@osadl.at> <2c43e965-9a12-0367-fb23-bedfaaed4f68@axentia.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c43e965-9a12-0367-fb23-bedfaaed4f68@axentia.se> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 04, 2018 at 01:49:11PM +0000, Peter Rosin wrote: > On 2018-12-04 13:13, Nicholas Mc Guire wrote: > > On Tue, Dec 04, 2018 at 11:16:59AM +0000, Peter Rosin wrote: > >> Hi! > >> > >> This patch looks like a good idea. However, a nitpick below. > >> > >> On 2018-12-01 11:01, Nicholas Mc Guire wrote: > >>> devm_kstrdup() may return NULL if internal allocation failed. > >>> Thus using name, value is unsafe without being checked. As > >>> i2c_demux_pinctrl_probe() can return -ENOMEM in other cases > >>> a dev_err() message is included to make the failure location > >>> clear. > >>> > >>> Signed-off-by: Nicholas Mc Guire > >>> Fixes: e35478eac030 ("i2c: mux: demux-pinctrl: run properly with multiple instances") > >>> --- > >>> > >>> Problem located with experimental coccinelle script > >>> > >>> Q: The use of devm_kstrdup() seems a bit odd while technically not wrong, > >>> personally I think devm_kasprintf() would be more suitable here. > >>> > >>> Patch was compile tested with: multi_v7_defconfig > >>> (implies I2C_DEMUX_PINCTRL=y) > >>> > >>> Patch is against 4.20-rc4 (localversion-next is next-20181130) > >>> > >>> drivers/i2c/muxes/i2c-demux-pinctrl.c | 6 ++++++ > >>> 1 file changed, 6 insertions(+) > >>> > >>> diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c > >>> index 035032e..c466999 100644 > >>> --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c > >>> +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c > >>> @@ -244,6 +244,12 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev) > >>> > >>> props[i].name = devm_kstrdup(&pdev->dev, "status", GFP_KERNEL); > >>> props[i].value = devm_kstrdup(&pdev->dev, "ok", GFP_KERNEL); > >>> + if (!props[i].name || !props[i].value) { > >>> + dev_err(&pdev->dev, > >>> + "chan %d name, value allocation failed\n", i); > >> > >> Please drop this memory allocation failure message. You should get such a > >> message from devm_kstrdup. > >> > > > > hm...tried to figure out where that message would be comming > > from - but I could not find any point in the call tree that > > would issue such a message ? > > > > devm_kstrdup() > > -> devm_kmalloc() > > -> alloc_dr() > > --> kmalloc_track_caller() (non-NUMA) > > | -> __kmalloc_node() > > | -> __do_kmalloc_node() > > `-> __kmalloc_node_track_caller() (NUMA) > > -> __do_kmalloc_node() > > > > __do_kmalloc_node() seems like it simply returns NULL but > > issues no failure message. > > Am I overlooking something ? > > Well, I don't know the details, but checkpatch will warn about simple > error messages on devm_kstrdup failure (if I read the checkpatch source > correctly). But in this case there are two parallel conditions in the > if and hence checkpatch stumbles, but gist is the same, you should not > sprinkle messages on memory allocation failure. > not in this case - atleast checkpatch --strict on the original patch did not issue any complaint to that ends. But yes - you are right that the intent in checkpatch is clear and this should not be carrying a failure message. thx! hofrat