From patchwork Thu Aug 8 00:06:58 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11082981 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 81038912 for ; Thu, 8 Aug 2019 00:09:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7013E28AAE for ; Thu, 8 Aug 2019 00:09:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6453E28AC6; Thu, 8 Aug 2019 00:09:40 +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=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL 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 E8D7828AAE for ; Thu, 8 Aug 2019 00:09:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730693AbfHHAHl (ORCPT ); Wed, 7 Aug 2019 20:07:41 -0400 Received: from mail-pl1-f202.google.com ([209.85.214.202]:32832 "EHLO mail-pl1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730681AbfHHAHk (ORCPT ); Wed, 7 Aug 2019 20:07:40 -0400 Received: by mail-pl1-f202.google.com with SMTP id f5so4485012plr.0 for ; Wed, 07 Aug 2019 17:07:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=F1VsQKe1CvGe90szBrckBeIyG/tsASbX2ypyWhc14LE=; b=qMlQjFH4LNkPFt7okSAYQH4LtgYOG/hpHDLWPX566YGyPNtYJPUP46rcks4c8eYnlb 0bNs4gihvrRlVOh7tP/Xx/1BqrbyEXSnnaOOpY9HI+9wJsc3wJD2PF5r/GwLRZeUaYMb amKeZJBCwihyM/juh7mpeQuNxOuwGxJ9NIxBA9znCQKrTU72jhbs+1l3EcTedt8WGozq BelKAb8SlmNg4vuZFYuqAK88knD3oJ0DDgpmSGebDO7s3E3QGb7ZbaHu1OLTTpwaG5sS F0qMtxQ/4l2MjyX8Z6GY0yoXhEMxtyJK+E73Gdo88OD3vLRca9iG/my2Faw6p3KXszOw kfgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=F1VsQKe1CvGe90szBrckBeIyG/tsASbX2ypyWhc14LE=; b=fki7KmJ45am/358P1eDSfjupd1TNr+lgZvf1us6CNM202LV4OLqUqtyjO297k0kEwQ Das31NU7qAh3zdgaId1Zm3ar8Za3cLRmoOvSH4QWppJdlP8d0IMBxJAAQo1FwqGCgYQJ vUvZhs0UjWNrfdm18IMLlHaX5e/tK/xeJSOJhVpcQciQru96VNUUjhaWP0hQHrJ9a91l fxr5oQnkOmqaSl/LByvP8mGgbiONGCTAnem0JUh7ppNdrh8FPN/SHcBW343YsdAsaGB/ vifYO49HTHZIn3xPtnrubMFTl9Pm41CrML8Vk68D6nAqv5dOvw9yromUKi2QlKJWvdiL x3rQ== X-Gm-Message-State: APjAAAWTkPrmsb73yeCHWfJmaUkvtHpeL05ZkiIUZ4CIqZ2A4yMk+Gid sP/zwLV4YbrMd/3kHoqZlG+pPgt23fnbIYnSj6HqXg== X-Google-Smtp-Source: APXvYqyhRtz7BIHwY/gc5z8qI7waq/52irPZx7U7/ay1YZFhLhsfUoUA1xgDlFmESnZc3tLh3+OeQj7gqeFdOTwZNMoaFQ== X-Received: by 2002:a65:6815:: with SMTP id l21mr10209698pgt.146.1565222859667; Wed, 07 Aug 2019 17:07:39 -0700 (PDT) Date: Wed, 7 Aug 2019 17:06:58 -0700 In-Reply-To: <20190808000721.124691-1-matthewgarrett@google.com> Message-Id: <20190808000721.124691-7-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190808000721.124691-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog Subject: [PATCH V38 06/29] kexec_load: Disable at runtime if the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , David Howells , Matthew Garrett , Dave Young , Kees Cook , kexec@lists.infradead.org Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Garrett The kexec_load() syscall 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_load() in this situation. This does not affect kexec_file_load() syscall which can check for a signature on the image to be booted. Signed-off-by: David Howells Signed-off-by: Matthew Garrett Acked-by: Dave Young Reviewed-by: Kees Cook cc: kexec@lists.infradead.org --- include/linux/security.h | 1 + kernel/kexec.c | 8 ++++++++ security/lockdown/lockdown.c | 1 + 3 files changed, 10 insertions(+) diff --git a/include/linux/security.h b/include/linux/security.h index 9458152601b5..69c5de539e9a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -105,6 +105,7 @@ enum lockdown_reason { LOCKDOWN_NONE, LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_DEV_MEM, + LOCKDOWN_KEXEC, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/kernel/kexec.c b/kernel/kexec.c index 1b018f1a6e0d..bc933c0db9bf 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -205,6 +205,14 @@ static inline int kexec_load_check(unsigned long nr_segments, if (result < 0) return result; + /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + result = security_locked_down(LOCKDOWN_KEXEC); + if (result) + return result; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index d2ef29d9f0b2..6f302c156bc8 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", + [LOCKDOWN_KEXEC] = "kexec of unsigned images", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };