From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933523AbeCMP4F (ORCPT ); Tue, 13 Mar 2018 11:56:05 -0400 Received: from mx2.suse.de ([195.135.220.15]:39859 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932400AbeCMP4D (ORCPT ); Tue, 13 Mar 2018 11:56:03 -0400 From: Petr Mladek To: Jiri Kosina , Josh Poimboeuf , Miroslav Benes Cc: Joe Lawrence , Jessica Yu , Nicolai Stange , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH 0/2] livepatch: Allocate and free shadow variables more safely Date: Tue, 13 Mar 2018 16:54:46 +0100 Message-Id: <20180313155448.1998-1-pmladek@suse.com> X-Mailer: git-send-email 2.13.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nikolai started to use shadow variables and found that list_head is not initialized correctly using the existing API. The problem is that LIST_HEAD_INIT() set pointers to itself. klp_shadow_alloc() then copies these pointers to another location. It would be possible to solve this by a late initialization. But this does not work well with klp_shadow_get_or_alloc(). Also this behavior is error prone. Note that list_head might be hidden in another structure, for example mutex. I suggest to change the API and allow to initialize the shadow variables using a custom callback. I think that we have already talked about this but we decided to go the easier way. It seems that it was a bad decision. I send also patch that add a symmetric callback to the klp_shadow_free() functions. It might be handy especially for klp_shadow_free_all(). The patchset is against the current Linus' tree. Petr Mladek (2): livepatch: Initialize shadow variables by init function safely livepatch: Allow to unregister or free shadow data using a custom function Documentation/livepatch/shadow-vars.txt | 42 ++++++++++++----- include/linux/livepatch.h | 23 +++++++--- kernel/livepatch/shadow.c | 75 +++++++++++++++++++++---------- samples/livepatch/livepatch-shadow-fix1.c | 44 +++++++++++++----- samples/livepatch/livepatch-shadow-fix2.c | 33 +++++++------- 5 files changed, 150 insertions(+), 67 deletions(-) -- 2.13.6