From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751356AbeDEMXf (ORCPT ); Thu, 5 Apr 2018 08:23:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:50508 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751038AbeDEMXe (ORCPT ); Thu, 5 Apr 2018 08:23:34 -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 v2 0/2] livepatch: Allocate and free shadow variables more safely Date: Thu, 5 Apr 2018 14:23:13 +0200 Message-Id: <20180405122315.29065-1-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(). Changes against v1: + Rename init/free callbacks to ctor/dtor + Misc update of comments and commit messages + Fix sizeof() in the sample code in shadow-vars.txt Petr Mladek (2): livepatch: Initialize shadow variables safely by a custom callback livepatch: Allow to call a custom callback when freeing shadow variables Documentation/livepatch/shadow-vars.txt | 41 +++++++---- include/linux/livepatch.h | 19 ++++-- kernel/livepatch/shadow.c | 109 ++++++++++++++++++++---------- samples/livepatch/livepatch-shadow-fix1.c | 43 +++++++++--- samples/livepatch/livepatch-shadow-fix2.c | 33 +++++---- 5 files changed, 164 insertions(+), 81 deletions(-) -- 2.13.6