From patchwork Wed Nov 16 21:48:07 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 9432855 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7A06C60471 for ; Wed, 16 Nov 2016 21:50:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6A85529140 for ; Wed, 16 Nov 2016 21:50:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5DA3A2916D; Wed, 16 Nov 2016 21:50:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A47E729168 for ; Wed, 16 Nov 2016 21:50:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938861AbcKPVsM (ORCPT ); Wed, 16 Nov 2016 16:48:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58224 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936594AbcKPVsJ (ORCPT ); Wed, 16 Nov 2016 16:48:09 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 524DE8A14F; Wed, 16 Nov 2016 21:48:09 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-116-110.phx2.redhat.com [10.3.116.110]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uAGLm7do022492; Wed, 16 Nov 2016 16:48:08 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 07/16] kexec: Disable at runtime if the kernel is locked down From: David Howells To: keyrings@vger.kernel.org Cc: dhowells@redhat.com, matthew.garrett@nebula.com, linux-security-module@vger.kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 16 Nov 2016 21:48:07 +0000 Message-ID: <147933288742.19316.17308231278815492742.stgit@warthog.procyon.org.uk> In-Reply-To: <147933283664.19316.12454053022687659937.stgit@warthog.procyon.org.uk> References: <147933283664.19316.12454053022687659937.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Wed, 16 Nov 2016 21:48:09 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Garrett kexec permits the loading and execution of arbitrary code in ring 0, which is something that lock-down is meant to prevent. It makes sense to disable kexec in this situation. This does not affect kexec_file_load() which can check for a signature on the image to be booted. Signed-off-by: Matthew Garrett Signed-off-by: David Howells --- kernel/kexec.c | 8 ++++++++ 1 file changed, 8 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/kernel/kexec.c b/kernel/kexec.c index 980936a90ee6..c6aa4620d1bf 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -194,6 +195,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, return -EPERM; /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + if (kernel_is_locked_down()) + return -EPERM; + + /* * Verify we have a legal set of flags * This leaves us room for future extensions. */