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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22F6BC04A68 for ; Wed, 27 Jul 2022 16:38:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238997AbiG0Qi1 (ORCPT ); Wed, 27 Jul 2022 12:38:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238729AbiG0Qhk (ORCPT ); Wed, 27 Jul 2022 12:37:40 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA5414D80A; Wed, 27 Jul 2022 09:28:21 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C430B61662; Wed, 27 Jul 2022 16:27:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEA94C433D6; Wed, 27 Jul 2022 16:27:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658939277; bh=o5uo9H+aQK80HuhfKYBHekHvHmapsv5dz6+d7wV1KCs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UY7SFRpt1ydRyZ8TedtGwRdOL4g4ZfP3SbmDcKKNEIpxqKhvelxvgrYQUjHjupd3r 7DkGoetRfO3IE+dXLN37xKsC+IylFBhYQYyocQH3quZKr0PmqxwOfQtHyozjjpZL7j hAMn5Unkz0r3Sk7QG3RdMc62YfgXWRtZuTFuP6s0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Snowberg , Mimi Zohar , John Haxby , Linus Torvalds Subject: [PATCH 5.4 04/87] lockdown: Fix kexec lockdown bypass with ima policy Date: Wed, 27 Jul 2022 18:09:57 +0200 Message-Id: <20220727161009.182304198@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220727161008.993711844@linuxfoundation.org> References: <20220727161008.993711844@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Snowberg commit 543ce63b664e2c2f9533d089a4664b559c3e6b5b upstream. The lockdown LSM is primarily used in conjunction with UEFI Secure Boot. This LSM may also be used on machines without UEFI. It can also be enabled when UEFI Secure Boot is disabled. One of lockdown's features is to prevent kexec from loading untrusted kernels. Lockdown can be enabled through a bootparam or after the kernel has booted through securityfs. If IMA appraisal is used with the "ima_appraise=log" boot param, lockdown can be defeated with kexec on any machine when Secure Boot is disabled or unavailable. IMA prevents setting "ima_appraise=log" from the boot param when Secure Boot is enabled, but this does not cover cases where lockdown is used without Secure Boot. To defeat lockdown, boot without Secure Boot and add ima_appraise=log to the kernel command line; then: $ echo "integrity" > /sys/kernel/security/lockdown $ echo "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig" > \ /sys/kernel/security/ima/policy $ kexec -ls unsigned-kernel Add a call to verify ima appraisal is set to "enforce" whenever lockdown is enabled. This fixes CVE-2022-21505. Cc: stable@vger.kernel.org Fixes: 29d3c1c8dfe7 ("kexec: Allow kexec_file() with appropriate IMA policy when locked down") Signed-off-by: Eric Snowberg Acked-by: Mimi Zohar Reviewed-by: John Haxby Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- security/integrity/ima/ima_policy.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -1542,6 +1542,10 @@ bool ima_appraise_signature(enum kernel_ if (id >= READING_MAX_ID) return false; + if (id == READING_KEXEC_IMAGE && !(ima_appraise & IMA_APPRAISE_ENFORCE) + && security_locked_down(LOCKDOWN_KEXEC)) + return false; + func = read_idmap[id] ?: FILE_CHECK; rcu_read_lock();