From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id T39cK+X6GFuzBAAAmS7hNA ; Thu, 07 Jun 2018 09:30:12 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 158F3607DC; Thu, 7 Jun 2018 09:30:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id 8E7AE606DD; Thu, 7 Jun 2018 09:30:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 8E7AE606DD Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753165AbeFGJ3y (ORCPT + 25 others); Thu, 7 Jun 2018 05:29:54 -0400 Received: from mx2.suse.de ([195.135.220.15]:54601 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751491AbeFGJ3w (ORCPT ); Thu, 7 Jun 2018 05:29:52 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 3C9A0ABF1; Thu, 7 Jun 2018 09:29:51 +0000 (UTC) From: Miroslav Benes To: jikos@kernel.org, jpoimboe@redhat.com, jeyu@kernel.org Cc: pmladek@suse.com, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Miroslav Benes Subject: [PATCH 0/3] Deny the patched modules to be removed Date: Thu, 7 Jun 2018 11:29:46 +0200 Message-Id: <20180607092949.1706-1-mbenes@suse.cz> X-Mailer: git-send-email 2.17.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting the second patch's changelog: Josh reported a bug: When the object to be patched is a module, and that module is rmmod'ed and reloaded, it fails to load with: module: x86/modules: Skipping invalid relocation target, existing value is nonzero for type 2, loc 00000000ba0302e9, val ffffffffa03e293c livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8) livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd' The livepatch module has a relocation which references a symbol in the _previous_ loading of nfsd. When apply_relocate_add() tries to replace the old relocation with a new one, it sees that the previous one is nonzero and it errors out. On ppc64le, we have a similar issue: module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd] livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8) livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd' He also proposed three different solutions. We could remove the error check in apply_relocate_add() introduced by commit eda9cec4c9a1 ("x86/module: Detect and skip invalid relocations"). However the check is useful for detecting corrupted modules. We could also reverse the relocation patching (clear all relocation targets on x86_64, or return back nops on powerpc) in klp_unpatch_object(). The solution is not universal and is too much arch-specific. We decided to deny the patched modules to be removed. If it proves to be a major drawback for users, we can still implement a different approach. There were many subtle details to check, so it may be broken somewhere. Hopefully it is not, but please review carefully. Miroslav Benes (3): livepatch: Nullify obj->mod in klp_module_coming()'s error path livepatch: Deny the patched modules to be removed module: Remove superfluous call to klp_module_going() kernel/livepatch/core.c | 25 +++++++++++++++++++++++-- kernel/module.c | 1 - 2 files changed, 23 insertions(+), 3 deletions(-) -- 2.17.0