From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DAF9F3D7D71; Tue, 21 Apr 2026 14:09:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776780572; cv=none; b=gMn82zFd8E4qtnrkRAtYqzkthH6kxsJskjhxfGTMkSzST6bjZo0XU7xWaVQUJsU+C7WsoohI/jRsAz0XtIUX8r+fsOuZyB3FoU3oLA5x6J0uU6qAHrwYhHUMlYbVA9fKAsDuitfV3D/QnhyQHX3uJeZdaRgSY64uPNJ3dmwzbqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776780572; c=relaxed/simple; bh=PM0r4vU3njSbwOSpmk+txAaJg1BVbJV8LhO5dpZzTXA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WVdY4yIiKvmxT85igZ9m05RnVdwRvSymGUwtZDQNAyRf11+9+CjuhU3wbbacOa2A6UzrMLQb7w3VIKeacDIv0VX2U9LuGUtvQKwwnp16enLl/CdxeeqA6bKavDqjSR9upOQ/EiS4jXl6oYyHCFyLljlwxjnTXGG8SW8fpQkhLXI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Aqpn6Rs6; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Aqpn6Rs6" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9411D25DC; Tue, 21 Apr 2026 07:09:23 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.1.197.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BE3763F915; Tue, 21 Apr 2026 07:09:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1776780568; bh=PM0r4vU3njSbwOSpmk+txAaJg1BVbJV8LhO5dpZzTXA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Aqpn6Rs6HdmexG8FiKGSHBbrKhhKVxm72mZiGAWnCbVyf1d+em6YjunDAfB22s/bS QQkYCu8FBISjfN4/0nJ/dGmsJsEA5WNXPJ/KK2n0K4lAWF96MweAYDOhli6QHxz8Lc MmQMD2rltRpMnrYoMqAktVh7FekpLbELIu7MJ2w0= Date: Tue, 21 Apr 2026 15:09:23 +0100 From: Yeoreum Yun To: Mimi Zohar Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, roberto.sassu@huawei.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, peterhuewe@gmx.de, jarkko@kernel.org, jgg@ziepe.ca, sudeep.holla@kernel.org, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org Subject: Re: [RFC PATCH 1/4] security: ima: move ima_init into late_initcall_sync Message-ID: References: <20260417175759.3191279-1-yeoreum.yun@arm.com> <20260417175759.3191279-2-yeoreum.yun@arm.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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Hi Mimi, > On Tue, 2026-04-21 at 13:50 +0100, Yeoreum Yun wrote: > > Hi Mimi, > > > > > On Fri, 2026-04-17 at 18:57 +0100, Yeoreum Yun wrote: > > > > To generate the boot_aggregate log in the IMA subsystem with TPM PCR values, > > > > the TPM driver must be built as built-in and > > > > must be probed before the IMA subsystem is initialized. > > > > > > > > However, when the TPM device operates over the FF-A protocol using > > > > the CRB interface, probing fails and returns -EPROBE_DEFER if > > > > the tpm_crb_ffa device — an FF-A device that provides the communication > > > > interface to the tpm_crb driver — has not yet been probed. > > > > > > > > To ensure the TPM device operating over the FF-A protocol with > > > > the CRB interface is probed before IMA initialization, > > > > the following conditions must be met: > > > > > > > > 1. The corresponding ffa_device must be registered, > > > > which is done via ffa_init(). > > > > > > > > 2. The tpm_crb_driver must successfully probe this device via > > > > tpm_crb_ffa_init(). > > > > > > > > 3. The tpm_crb driver using CRB over FF-A can then > > > > be probed successfully. (See crb_acpi_add() and > > > > tpm_crb_ffa_init() for reference.) > > > > > > > > Unfortunately, ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init() are > > > > all registered with device_initcall, which means crb_acpi_driver_init() may > > > > be invoked before ffa_init() and tpm_crb_ffa_init() are completed. > > > > > > > > When this occurs, probing the TPM device is deferred. > > > > However, the deferred probe can happen after the IMA subsystem > > > > has already been initialized, since IMA initialization is performed > > > > during late_initcall, and deferred_probe_initcall() is performed > > > > at the same level. > > > > > > > > To resolve this, move ima_init() into late_inicall_sync level > > > > so that let IMA not miss TPM PCR value when generating boot_aggregate > > > > log though TPM device presents in the system. > > > > > > > > Signed-off-by: Yeoreum Yun > > > > > > IMA should be initialized as early as possible. I'm really hesitant to defer > > > ima_init() to late_initcall_sync() for systems that the TPM is currently > > > initialized in time. For these systems, continue initializing IMA at > > > late_initcall(). As a compromise for those systems that the TPM isn't properly > > > initialized in time, define and instantiate the late_initcall_sync(). > > > > > > ima_init() would need to differentiate between the late_initcall and > > > late_initcall_sync. On late_initcall(), instead of saying "No TPM chip found, > > > activating TPM-bypass!", it should say "No TPM chip found, deferring to > > > late_initcall_sync" or something similar. > > > > But can we really move those initialisations to be called again? > > > > I am referring to functions such as ima_init_crypto(), > > ima_add_boot_aggregate(), and ima_measure_critical_data() in ima_init()— > > first without TPM, and then a second time once TPM becomes available. > > I don’t think that approach would work. > > > > In other words, unless tpm_default_chip() can differentiate between a TPM > > device that is deferred and one that does not exist, we cannot distinguish > > between the “defer” case and “-EEXIST”. > > > > It might be possible if the TPM core tracked the state when a driver returns > > -EPROBE_DEFER, but I am not sure that is the right approach. > > For deferred probe cases, the “device initialised in time” check should > > likely be done at late_initcall_sync, rather than late_initcall. > > > > This implies that any such check performed before late_initcall_sync > > does not reflect a valid state, as it cannot distinguish between “not > > present” and “deferred”. > > > > Therefore, I think the TPM check in IMA should be performed at > > late_initcall_sync. > > > > > > Am I missing something? > > In ima_init() you short circuit out, when called by late_initcall(), if the TPM > hasn't been initialized. So the rest of the ima_init() isn't called. Roughly > something like this (needs some cleanup): > > int __init ima_init(void) > { > static int first = 1; > int rc; > > if (ima_tpm_chip) > return 0; > > ima_tpm_chip = tpm_default_chip(); > if (!ima_tpm_chip && first) { > pr_info("No TPM chip found, deferring te late_initcall_sync()\n"); > first = 0; > return 0; > } I see. then I'll respin in v2. Thanks! -- Sincerely, Yeoreum Yun