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=-8.4 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 730ECC65BAE for ; Thu, 13 Dec 2018 14:01:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D27420849 for ; Thu, 13 Dec 2018 14:01:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D27420849 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 S1729567AbeLMOBE (ORCPT ); Thu, 13 Dec 2018 09:01:04 -0500 Received: from 178.115.242.59.static.drei.at ([178.115.242.59]:52285 "EHLO mail.osadl.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729430AbeLMOBD (ORCPT ); Thu, 13 Dec 2018 09:01:03 -0500 Received: by mail.osadl.at (Postfix, from userid 1001) id 0BE9F5C22C4; Thu, 13 Dec 2018 15:00:58 +0100 (CET) Date: Thu, 13 Dec 2018 15:00:58 +0100 From: Nicholas Mc Guire To: Petr Mladek Cc: Nicholas Mc Guire , Josh Poimboeuf , Jessica Yu , Jiri Kosina , Miroslav Benes , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] livepatch: handle kzalloc failure Message-ID: <20181213140057.GA29272@osadl.at> References: <1544699390-15673-1-git-send-email-hofrat@osadl.org> <20181213123139.oukmwpkw2yfap6oa@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181213123139.oukmwpkw2yfap6oa@pathway.suse.cz> 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 Thu, Dec 13, 2018 at 01:31:39PM +0100, Petr Mladek wrote: > On Thu 2018-12-13 12:09:49, Nicholas Mc Guire wrote: > > kzalloc() return should always be checked - notably in example code > > where this may be seen as reference. On failure of allocation > > livepatch_fix1_dummy_alloc() should return NULL. > > > > Signed-off-by: Nicholas Mc Guire > > --- > > > > Problem was located with an experimental coccinelle script > > > > Patch was compile tested with: x86_64_defconfig + FTRACE=y > > FUNCTION_TRACER=y, EXPERT=y, LATENCYTOP=y, SAMPLES=y, SAMPLE_LIVEPATCH=y > > (with some unrelated sparse warnings on symbols not being static) > > > > Patch is against 4.20-rc6 (localversion-next is next-20181213) > > > > samples/livepatch/livepatch-shadow-fix1.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/samples/livepatch/livepatch-shadow-fix1.c b/samples/livepatch/livepatch-shadow-fix1.c > > index 49b1355..a0e8f04 100644 > > --- a/samples/livepatch/livepatch-shadow-fix1.c > > +++ b/samples/livepatch/livepatch-shadow-fix1.c > > @@ -89,6 +89,9 @@ struct dummy *livepatch_fix1_dummy_alloc(void) > > * pointer to handle resource release. > > */ > > leak = kzalloc(sizeof(int), GFP_KERNEL); > > + if (!leak) > > + return NULL; > > It should be: > > if (!leak) { > kfree(d); > return NULL; > } > > Note that The check is not strictly needed in this artificial > example because we never read/write any data there. But I agree > that we should add the check to promote the the right programming > patterns. > thanks for catching this ! will send a V2. thx! hofrat