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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 95594C35247 for ; Wed, 5 Feb 2020 22:39:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 745AF24672 for ; Wed, 5 Feb 2020 22:39:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727594AbgBEWjn (ORCPT ); Wed, 5 Feb 2020 17:39:43 -0500 Received: from mga02.intel.com ([134.134.136.20]:60116 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727538AbgBEWji (ORCPT ); Wed, 5 Feb 2020 17:39:38 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 14:39:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="225092462" Received: from unknown (HELO localhost.jf.intel.com) ([10.54.75.26]) by fmsmga007.fm.intel.com with ESMTP; 05 Feb 2020 14:39:37 -0800 From: Kristen Carlson Accardi To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org Cc: rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Kristen Carlson Accardi Subject: [RFC PATCH 09/11] kallsyms: hide layout and expose seed Date: Wed, 5 Feb 2020 14:39:48 -0800 Message-Id: <20200205223950.1212394-10-kristen@linux.intel.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com> References: <20200205223950.1212394-1-kristen@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To support finer grained kaslr (fgkaslr), we need to make a couple changes to kallsyms. Firstly, we need to hide our sorted list of symbols, since this will give away our new layout. Secondly, we will export the seed used for randomizing the layout so that it can be used to make a particular layout persist across boots for debug purposes. Signed-off-by: Kristen Carlson Accardi --- kernel/kallsyms.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 136ce049c4ad..432b13a3a033 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -698,6 +698,21 @@ const char *kdb_walk_kallsyms(loff_t *pos) } #endif /* CONFIG_KGDB_KDB */ +#ifdef CONFIG_FG_KASLR +extern const u64 fgkaslr_seed[] __weak; + +static int proc_fgkaslr_show(struct seq_file *m, void *v) +{ + seq_printf(m, "%llx\n", fgkaslr_seed[0]); + seq_printf(m, "%llx\n", fgkaslr_seed[1]); + seq_printf(m, "%llx\n", fgkaslr_seed[2]); + seq_printf(m, "%llx\n", fgkaslr_seed[3]); + return 0; +} +#else +static inline int proc_fgkaslr_show(struct seq_file *m, void *v) { return 0; } +#endif + static const struct file_operations kallsyms_operations = { .open = kallsyms_open, .read = seq_read, @@ -707,7 +722,20 @@ static const struct file_operations kallsyms_operations = { static int __init kallsyms_init(void) { - proc_create("kallsyms", 0444, NULL, &kallsyms_operations); + /* + * When fine grained kaslr is enabled, we don't want to + * print out the symbols even with zero pointers because + * this reveals the randomization order. If fg kaslr is + * enabled, make kallsyms available only to privileged + * users. + */ + if (!IS_ENABLED(CONFIG_FG_KASLR)) + proc_create("kallsyms", 0444, NULL, &kallsyms_operations); + else { + proc_create_single("fgkaslr_seed", 0400, NULL, + proc_fgkaslr_show); + proc_create("kallsyms", 0400, NULL, &kallsyms_operations); + } return 0; } device_initcall(kallsyms_init); -- 2.24.1