From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C081C46475 for ; Thu, 25 Oct 2018 09:00:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6FA220840 for ; Thu, 25 Oct 2018 09:00:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6FA220840 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726866AbeJYRc0 (ORCPT ); Thu, 25 Oct 2018 13:32:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:44828 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726587AbeJYRcZ (ORCPT ); Thu, 25 Oct 2018 13:32:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E6D7EAF6F; Thu, 25 Oct 2018 09:00:34 +0000 (UTC) Date: Thu, 25 Oct 2018 11:00:33 +0200 (CEST) From: Miroslav Benes To: Petr Mladek cc: Jessica Yu , Torsten Duwe , Will Deacon , Catalin Marinas , Julien Thierry , Steven Rostedt , Josh Poimboeuf , Ingo Molnar , Ard Biesheuvel , Arnd Bergmann , AKASHI Takahiro , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [PATCH] arm64/module: use mod->klp_info section header information In-Reply-To: <20181025080816.525dppcfrrevf6jc@pathway.suse.cz> Message-ID: References: <20181001140910.086E768BC7@newverein.lst.de> <20181001141652.5478C68BE1@newverein.lst.de> <20181023175553.gaobskk26koft6s2@linux-8ccs> <20181025080816.525dppcfrrevf6jc@pathway.suse.cz> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 25 Oct 2018, Petr Mladek wrote: > On Tue 2018-10-23 19:55:54, Jessica Yu wrote: > > The arm64 module loader keeps a pointer into info->sechdrs to keep track > > of section header information for .plt section(s). A pointer to the > > relevent section header (struct elf64_shdr) in info->sechdrs is stored > > in mod->arch.{init,core}.plt. This pointer may be accessed while > > applying relocations in apply_relocate_add() for example. And unlike > > normal modules, livepatch modules can call apply_relocate_add() after > > module load. But the info struct (and therefore info->sechdrs) gets > > freed at the end of load_module() and so mod->arch.{init,core}.plt > > becomes an invalid pointer after the module is done loading. > > > > Luckily, livepatch modules already keep a copy of Elf section header > > information in mod->klp_info. So make sure livepatch modules on arm64 > > have access to the section headers in klp_info and set > > mod->arch.{init,core}.plt to the appropriate section header in > > mod->klp_info so that they can call apply_relocate_add() even after > > module load. > > > > diff --git a/kernel/module.c b/kernel/module.c > > index f475f30eed8c..f3ac04cc9fc3 100644 > > --- a/kernel/module.c > > +++ b/kernel/module.c > > @@ -3367,6 +3367,8 @@ int __weak module_finalize(const Elf_Ehdr *hdr, > > > > static int post_relocation(struct module *mod, const struct load_info *info) > > { > > + int err; > > + > > /* Sort exception table now relocations are done. */ > > sort_extable(mod->extable, mod->extable + mod->num_exentries); > > > > @@ -3377,8 +3379,18 @@ static int post_relocation(struct module *mod, const struct load_info *info) > > /* Setup kallsyms-specific fields. */ > > add_kallsyms(mod, info); > > > > + if (is_livepatch_module(mod)) { > > + err = copy_module_elf(mod, info); > > + if (err < 0) > > + return err; > > + } > > + > > /* Arch-specific module finalizing. */ > > - return module_finalize(info->hdr, info->sechdrs, mod); > > + err = module_finalize(info->hdr, info->sechdrs, mod); > > + if (err < 0) > > if (err < 0 && is_livepatch_module(mod)) Ah, right. > > + free_module_elf(mod); > > + > > + return err; > > } > > Also we need to free the copied stuff in load_module() when > anything called after post_relocation() fails. I think > that the following would work: > > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3823,6 +3823,8 @@ static int load_module(struct load_info *info, const char __user *uargs, > kfree(mod->args); > free_arch_cleanup: > module_arch_cleanup(mod); > + if (is_livepatch_module(mod)) > + free_module_elf(mod); > free_modinfo: > free_modinfo(mod); > free_unload: Yes, we need to free it somewhere and I missed it. free_arch_cleanup seems to be the correct place. > But I suggest to just move copy_module_elf() up and keep > calling it from load_module() directly. It would make > the error handling more clear. Unfortunately it is not that simple. arm64's module_finalize() uses mod->klp_info with the patch, so copy_module_elf() must be called before. We could move module_finalize() from post_relocation() to load_module() and place copy_module_elf() between those two, but I don't know. That's up to Jessica. Miroslav