From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E437B15696E for ; Mon, 24 Feb 2025 01:37:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740361024; cv=none; b=MZrS3/AjjxeBkmT4ZGNzJjn+1JhgKt3VlzQEWwq5lUGn2WGAlwVe8CmwRy4Juy+ieHWRUN9SS05LVdu7cYGNcHwsLrc4mEhsq4D6fT0yquRxCAwThAKhliupoT0j9Q5YGfr3tllzbtPB8HI03bYSTCl+puPeE38VSG5VJ2pURJU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740361024; c=relaxed/simple; bh=Li8kSv3uGeFBd+kUVPcEx4w+EuTqJF/eS6zd+7ft5Sc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sE954OwyqHPAHHid+izi3OjjdXgOFms1WTe8wPtwOFpZcnVg9I/jAdCSCQWrGMou3R9faFM00bDZ3wgTIcDwqOxcGLqnLgLoMsKQlatmOGl+7Miq7+Z84coLiY9GisHQrWYYl80oCp62CZqCZ8+vQILDD+j96WxJUon499YMwvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=MFUf6dl/; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="MFUf6dl/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740361021; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ak1ca6nvXR4gpIUt8nNdn7G0ahaANyhsMag+O/8d/Is=; b=MFUf6dl/kHwA6Oz1rttYxwqjbFXvFUGxX0NV5WtDUVGYCqXgoYSgvT4Vl+GMxJZAgbSAHQ aSiHg0LbHrQWnXlQ++GLL9mqohh0Fb5kQlStQjYm4LQWdcV2SWRZsoTjdOibyHzP1ZgIpI psO+4wfhHl0sN3RlyuJTJhf0BMNd1Zs= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-269-IHleUlDoO_qBwyXkEEzRBQ-1; Sun, 23 Feb 2025 20:36:57 -0500 X-MC-Unique: IHleUlDoO_qBwyXkEEzRBQ-1 X-Mimecast-MFC-AGG-ID: IHleUlDoO_qBwyXkEEzRBQ_1740361015 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A18731800268; Mon, 24 Feb 2025 01:36:55 +0000 (UTC) Received: from localhost (unknown [10.72.112.127]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7C01D1800358; Mon, 24 Feb 2025 01:36:52 +0000 (UTC) Date: Mon, 24 Feb 2025 09:36:48 +0800 From: Baoquan He To: akpm@linux-foundation.org Cc: kexec@lists.infradead.org, Ondrej Kozina , Milan Broz , Thomas Staudt , Daniel P =?iso-8859-1?Q?=2E_Berrang=E9?= , Kairui Song , Pingfan Liu , Dave Young , linux-kernel@vger.kernel.org, x86@kernel.org, Dave Hansen , Vitaly Kuznetsov , Coiby Xu Subject: Re: [PATCH v8 0/7] Support kdump with LUKS encryption by reusing LUKS volume keys Message-ID: References: <20250207080818.129165-1-coxu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Hi Andrew, On 02/11/25 at 06:25pm, Baoquan He wrote: > On 02/07/25 at 04:08pm, Coiby Xu wrote: > > LUKS is the standard for Linux disk encryption, widely adopted by users, > > and in some cases, such as Confidential VMs, it is a requirement. With > > kdump enabled, when the first kernel crashes, the system can boot into > > the kdump/crash kernel to dump the memory image (i.e., /proc/vmcore) > > to a specified target. However, there are two challenges when dumping > > vmcore to a LUKS-encrypted device: > > > > - Kdump kernel may not be able to decrypt the LUKS partition. For some > > machines, a system administrator may not have a chance to enter the > > password to decrypt the device in kdump initramfs after the 1st kernel > > crashes; For cloud confidential VMs, depending on the policy the > > kdump kernel may not be able to unseal the keys with TPM and the > > console virtual keyboard is untrusted. > > > > - LUKS2 by default use the memory-hard Argon2 key derivation function > > which is quite memory-consuming compared to the limited memory reserved > > for kdump. Take Fedora example, by default, only 256M is reserved for > > systems having memory between 4G-64G. With LUKS enabled, ~1300M needs > > to be reserved for kdump. Note if the memory reserved for kdump can't > > be used by 1st kernel i.e. an user sees ~1300M memory missing in the > > 1st kernel. > > > > Besides users (at least for Fedora) usually expect kdump to work out of > > the box i.e. no manual password input or custom crashkernel value is > > needed. And it doesn't make sense to derivate the keys again in kdump > > kernel which seems to be redundant work. > > > > This patch set addresses the above issues by making the LUKS volume keys > > persistent for kdump kernel with the help of cryptsetup's new APIs > > (--link-vk-to-keyring/--volume-key-keyring). Here is the life cycle of > > the kdump copies of LUKS volume keys, > > > > 1. After the 1st kernel loads the initramfs during boot, systemd > > use an user-input passphrase to de-crypt the LUKS volume keys > > or TPM-sealed key and then save the volume keys to specified keyring > > (using the --link-vk-to-keyring API) and the key will expire within > > specified time. > > > > 2. A user space tool (kdump initramfs loader like kdump-utils) create > > key items inside /sys/kernel/config/crash_dm_crypt_keys to inform > > the 1st kernel which keys are needed. > > > > 3. When the kdump initramfs is loaded by the kexec_file_load > > syscall, the 1st kernel will iterate created key items, save the > > keys to kdump reserved memory. > > > > 4. When the 1st kernel crashes and the kdump initramfs is booted, the > > kdump initramfs asks the kdump kernel to create a user key using the > > key stored in kdump reserved memory by writing yes to > > /sys/kernel/crash_dm_crypt_keys/restore. Then the LUKS encrypted > > device is unlocked with libcryptsetup's --volume-key-keyring API. > > > > 5. The system gets rebooted to the 1st kernel after dumping vmcore to > > the LUKS encrypted device is finished > > > > After libcryptsetup saving the LUKS volume keys to specified keyring, > > whoever takes this should be responsible for the safety of these copies > > of keys. The keys will be saved in the memory area exclusively reserved > > for kdump where even the 1st kernel has no direct access. And further > > more, two additional protections are added, > > - save the copy randomly in kdump reserved memory as suggested by Jan > > - clear the _PAGE_PRESENT flag of the page that stores the copy as > > suggested by Pingfan > > > > This patch set only supports x86. There will be patches to support other > > architectures once this patch set gets merged. Could you pick this patchset into your tree since no conern from other reviewers? Thanks Baoquan > > This v8 looks good to me, thanks for the great effort, Coiby. > > Acked-by: Baoquan He >