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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 BAF97C3A59B for ; Fri, 30 Aug 2019 17:12:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A78023407 for ; Fri, 30 Aug 2019 17:12:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727959AbfH3RMv (ORCPT ); Fri, 30 Aug 2019 13:12:51 -0400 Received: from mga04.intel.com ([192.55.52.120]:14658 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727304AbfH3RMu (ORCPT ); Fri, 30 Aug 2019 13:12:50 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Aug 2019 10:12:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,447,1559545200"; d="scan'208";a="265378402" Received: from yyu32-desk1.sc.intel.com ([10.144.153.205]) by orsmga001.jf.intel.com with ESMTP; 30 Aug 2019 10:12:49 -0700 Message-ID: <5ddd0306f42c2b53ffbd8ee8c9b948c1d529cf98.camel@intel.com> Subject: Re: [RFC PATCH v2 2/2] ELF: Add ELF program property parsing support From: Yu-cheng Yu To: Dave Martin , Kees Cook Cc: "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , Thomas Gleixner , Jann Horn , "H.J. Lu" , Eugene Syromiatnikov , Florian Weimer , Peter Zijlstra Date: Fri, 30 Aug 2019 10:03:27 -0700 In-Reply-To: <20190830083415.GI27757@arm.com> References: <1566581020-9953-1-git-send-email-Dave.Martin@arm.com> <1566581020-9953-3-git-send-email-Dave.Martin@arm.com> <201908292224.007EB4D5@keescook> <20190830083415.GI27757@arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-08-30 at 09:34 +0100, Dave Martin wrote: > On Fri, Aug 30, 2019 at 06:37:45AM +0100, Kees Cook wrote: > > On Fri, Aug 23, 2019 at 06:23:40PM +0100, Dave Martin wrote: > > > ELF program properties will needed for detecting whether to enable > > > optional architecture or ABI features for a new ELF process. > > > > > > For now, there are no generic properties that we care about, so do > > > nothing unless CONFIG_ARCH_USE_GNU_PROPERTY=y. > > > > > > Otherwise, the presence of properties using the PT_PROGRAM_PROPERTY > > > phdrs entry (if any), and notify each property to the arch code. > > > > > > For now, the added code is not used. > > > > > > Signed-off-by: Dave Martin > > > > Reviewed-by: Kees Cook > > Thanks for the review. > > Do you have any thoughts on Yu-Cheng Yu's comments? It would be nice to > early-terminate the scan if we can, but my feeling so far was that the > scan is cheap, the number of properties is unlikely to be more than a > smallish integer, and the code separation benefits of just calling the > arch code for every property probably likely outweigh the costs of > having to iterate over every property. We could always optimise it > later if necessary. > > I need to double-check that there's no way we can get stuck in an > infinite loop with the current code, though I've not seen it in my > testing. I should throw some malformed notes at it though. Here is my arch_parse_elf_property() and objdump of the property. The parser works fine. Thanks, Yu-cheng int arch_parse_elf_property(u32 type, const void *data, size_t datasz, bool compat, struct arch_elf_state *state) { if (type != GNU_PROPERTY_X86_FEATURE_1_AND) return -ENOENT; if (datasz < sizeof(unsigned int)) return -ENOEXEC; state->gnu_property = *(unsigned int *)data; return 0; } Contents of section .note.gnu.property: 400338 04000000 30000000 05000000 474e5500 ....0.......GNU. 400348 020000c0 04000000 03000000 00000000 ................ 400358 000001c0 04000000 00000000 00000000 ................ 400368 010001c0 04000000 01000000 00000000 ................