From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753035AbcD1SVh (ORCPT ); Thu, 28 Apr 2016 14:21:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46339 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752625AbcD1SVf (ORCPT ); Thu, 28 Apr 2016 14:21:35 -0400 Date: Thu, 28 Apr 2016 14:21:31 -0400 From: Jessica Yu To: Miroslav Benes Cc: jpoimboe@redhat.com, jikos@kernel.org, pmladek@suse.com, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: klp: make object/func-walking helpers more robust Message-ID: <20160428182131.GA22885@packer-debian-8-amd64.digitalocean.com> References: <1461854048-31473-1-git-send-email-mbenes@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <1461854048-31473-1-git-send-email-mbenes@suse.cz> X-OS: Linux eisen.io 3.16.0-4-amd64 x86_64 User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Miroslav Benes [28/04/16 16:34 +0200]: >Current object-walking helper checks the presence of obj->funcs to >determine the end of objs array in klp_object structure. This is >somewhat fragile because one can easily forget about funcs definition >during livepatch creation. In such a case the livepatch module is >successfully loaded and all objects after the incorrect one are omitted. >This is very confusing. Let's make the helper more robust and check also >for the other external member, name. Thus the helper correctly stops on >an empty item of the array. We need to have a check for obj->funcs in >klp_init_object() to make it work. > >The same applies to a func-walking helper. > >As a benefit we'll check for new_func member definition during the >livepatch initialization. There is no such check anywhere in the code >now. > >Signed-off-by: Miroslav Benes >--- > include/linux/livepatch.h | 6 ++++-- > kernel/livepatch/core.c | 3 +++ > 2 files changed, 7 insertions(+), 2 deletions(-) > >diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h >index 0933ca47791c..a93a0b23dc8d 100644 >--- a/include/linux/livepatch.h >+++ b/include/linux/livepatch.h >@@ -104,10 +104,12 @@ struct klp_patch { > }; > > #define klp_for_each_object(patch, obj) \ >- for (obj = patch->objs; obj->funcs; obj++) >+ for (obj = patch->objs; obj->funcs || obj->name; obj++) Remember that for patches to vmlinux, obj->name and obj->mod will also both be NULL. So if someone happens to forget to fill in obj->funcs for a vmlinux patch, we won't catch that case here. Perhaps we need a better way of determining whether we've reached the end of the array, or determining that the struct is truly empty.. Jessica