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 46973C04A68 for ; Wed, 27 Jul 2022 17:02:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241258AbiG0RCX (ORCPT ); Wed, 27 Jul 2022 13:02:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232795AbiG0RBq (ORCPT ); Wed, 27 Jul 2022 13:01:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 953CB6BC1C; Wed, 27 Jul 2022 09:38:07 -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 53190601BE; Wed, 27 Jul 2022 16:38:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F294C433D6; Wed, 27 Jul 2022 16:38:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658939886; bh=T5DNPEG6pVCv0mZuUdiT16dtsq5c62BWvkJUSFQFrys=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VcfniOkNvxFybIufn7OSF2YR/ykBrUwy5zcb3YzGAHWJr0LycKPvNG/kf05sFSXgV anOBOlqUjq6E+YRcQrSlXGT841ooU6aBqkQkNoq2I5XRmXn08b76bhp7/XOXkUu86b Qpcap6eshuJT45+jFnqOJXSMvalzKZ5q2jrSTrPM= 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 5.15 004/201] lockdown: Fix kexec lockdown bypass with ima policy Date: Wed, 27 Jul 2022 18:08:28 +0200 Message-Id: <20220727161027.136489560@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220727161026.977588183@linuxfoundation.org> References: <20220727161026.977588183@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 @@ -2034,6 +2034,10 @@ 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();