From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754779AbeDPLg5 (ORCPT ); Mon, 16 Apr 2018 07:36:57 -0400 Received: from mx2.suse.de ([195.135.220.15]:36792 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754103AbeDPLgz (ORCPT ); Mon, 16 Apr 2018 07:36:55 -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 v3 0/2] livepatch: Allocate and free shadow variables more safely Date: Mon, 16 Apr 2018 13:36:45 +0200 Message-Id: <20180416113647.25288-1-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 v2: + Use pr_err() instead of WARN() when ctor() fails [Josh] + Some typos [Mirek] 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 | 108 ++++++++++++++++++++---------- samples/livepatch/livepatch-shadow-fix1.c | 43 +++++++++--- samples/livepatch/livepatch-shadow-fix2.c | 33 ++++----- 5 files changed, 163 insertions(+), 81 deletions(-) -- 2.13.6