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b=TyOt5i9tYthd4G0i8dKTDJi3Vb PHcYR+ZbkNiRyxhIeVaov+eGq9F6VBp9q87xmDxR06u0R9kBM+RMcQh4+OcF1ck2cYB96EtJAccUa 8wFCT8V+yW+MCR9gIXkgV48PPdMtuvhC8/kxfe/wPFvLwGWUZ3HYl13tuRwIIdwmHUmesQBOjwLL4 AcWa94J7ZH0C2qjoshpv/oeiopSMAETDlKCTyC2EaKo5wA8EEwWbiHpo8UbJGoF4Tg+E65whq4rEF KnnXZ5TuJ9mardaFWxy62xhM9N77HTb8Ml3fRKXZ9SnUdgVuToqO1pTphVgQQS0/rCNicG1Tgm186 eIX49kXg==; Received: from noodles by the.earth.li with local (Exim 4.98.2) (envelope-from ) id 1wFxS5-00000003kgC-1z1T; Thu, 23 Apr 2026 18:02:57 +0100 Date: Thu, 23 Apr 2026 18:02:57 +0100 From: Jonathan McDowell To: Mimi Zohar Cc: Yeoreum Yun , 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, 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, noodles@meta.com, sebastianene@google.com Subject: Re: [RFC PATCH v2 1/4] security: ima: call ima_init() again at late_initcall_sync for defered TPM Message-ID: References: <82803bb3b471898a77084c449b73c7f7b4eb2149.camel@linux.ibm.com> <56a8aab50a3b5ce0a345fc2079fb2abc7d0f1b23.camel@linux.ibm.com> <2866f7679fe6933de667ce74ae68bd4ea9198e2a.camel@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2866f7679fe6933de667ce74ae68bd4ea9198e2a.camel@linux.ibm.com> On Thu, Apr 23, 2026 at 10:48:49AM -0400, Mimi Zohar wrote: >On Thu, 2026-04-23 at 15:03 +0100, Jonathan McDowell wrote: >> On Thu, Apr 23, 2026 at 02:55:14PM +0100, Yeoreum Yun wrote: >> > > On Thu, 2026-04-23 at 13:53 +0100, Jonathan McDowell wrote: >> > > > On Thu, Apr 23, 2026 at 01:34:13PM +0100, Yeoreum Yun wrote: >> > > > > > > On Thu, 2026-04-23 at 06:55 +0100, Yeoreum Yun wrote: >> > > > > > > > > On Wed, 2026-04-22 at 20:41 +0100, Yeoreum Yun wrote: >> > > > > > > > > > > Hi Mimi, >> > > > > > > > > > > >> > > > > > > > > > > > On Wed, 2026-04-22 at 17:24 +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, call ima_init() again at 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 >> > > > > > > > > > > > >> > > > > > > > > > > > A lot of change for just detecting whether ima_init() is being called on >> > > > > > > > > > > > late_initcall or late_initcall_sync(), without any explanation for all the other >> > > > > > > > > > > > changes (e.g. ima_init_core). >> > > > > > > > > > > > >> > > > > > > > > > > > Please just limit the change to just calling ima_init() twice. >> > > > > > > > > > > >> > > > > > > > > > > My concern is that ima_update_policy_flags() will be called >> > > > > > > > > > > when ima_init() is deferred -- not initialised anything. >> > > > > > > > > > > though functionally, it might be okay however, >> > > > > > > > > > > I think ima_update_policy_flags() and notifier should work after ima_init() >> > > > > > > > > > > works logically. >> > > > > > > > > > > >> > > > > > > > > > > This change I think not much quite a lot. just wrapper ima_init() with >> > > > > > > > > > > ima_init_core() with some error handling. >> > > > > > > > > > > >> > > > > > > > > > > Am I missing something? >> > > > > > > > > > >> > > > > > > > > > Also, if we handle in ima_init() only, but it failed with other reason, >> > > > > > > > > > we shouldn't call again ima_init() in the late_initcall_sync. >> > > > > > > > > > >> > > > > > > > > > To handle this, It wouldn't do in the ima_init() but we need to handle >> > > > > > > > > > it by caller of ima_init(). >> > > > > > > > > >> > > > > > > > > Only tpm_default_chip() is being called to set the ima_tpm_chip. On failure, >> > > > > > > > > instead of going into TPM-bypass mode, return immediately. There are no calls >> > > > > > > > > to anything else. Just call ima_init() a second time. >> > > > > > > > >> > > > > > > > I’m not fully convinced this is sufficient. >> > > > > > > > >> > > > > > > > What I meant is the case where ima_init() fails due to other >> > > > > > > > initialisation steps, not only tpm_default_chip() (e.g. ima_fs_init()). >> > > > > > > >> > > > > > > The purpose of THIS patch is to add late_initcall_sync, when the TPM is not >> > > > > > > available at late_initcall. This would be classified as a bug fix and would be >> > > > > > > backported. No other changes should be included in this patch. >> > > > > > >> > > > > > Okay. >> > > > > > >> > > > > > > > >> > > > > > > > I’d also like to ask again whether it is fine to call >> > > > > > > > ima_update_policy_flags() and keep the notifier registered in the >> > > > > > > > deferred TPM case. While this may be functionally acceptable, it seems >> > > > > > > > logically questionable to do so when ima_init() has not completed. >> > > > > > > >> > > > > > > Other than extending the TPM, IMA should behave exactly the same whether there >> > > > > > > is a TPM or goes into TPM-bypass mode. >> > > > > > > >> > > > > > > > >> > > > > > > > There is also a possibility that a deferred case ultimately fails (e.g. >> > > > > > > > deferred at late_initcall, but then failing at late_initcall_sync >> > > > > > > > for another reason, even while entering TPM bypass mode). In that case, >> > > > > > > > it seems more appropriate to handle this state in the caller of >> > > > > > > > ima_init(), rather than inside ima_init() itself. >> > > > > > > >> > > > > > > If the TPM isn't found at late_initcall_sync(), then IMA should go into TPM- >> > > > > > > bypass mode. Please don't make any other changes to the existing IMA behavior >> > > > > > > and hide it here behind the late_initcall_sync change. >> > > > > > >> > > > > > Okay. you're talking called ima_update_policy_flags() at late_initcall >> > > > > > wouldn't be not a problem even in case of late_initcall_sync's ima_init() >> > > > > > get failed with "TPM-bypass mode". >> > > > > > >> > > > > > I see then, I'll make a patch simpler then. >> > > > > >> > > > > But I think in case of below situation: >> > > > > - late_initcall's first ima_init() is deferred. >> > > > > - late_initcall_sync try again but failed and try again with >> > > > > CONFIG_IMA_DEFAULT_HASH. >> > > > > >> > > > > I would like to sustain init_ima_core to reduce the same code repeat >> > > > > in late_initcall_sync. >> > > > >> > > > I think what Mimi's proposing is: >> > > > >> > > > If we're in late_initcall, and the TPM isn't available, return >> > > > immediately with an error (the EPROBE_DEFER?), don't do any init. >> > > > >> > > > If we're in late_initcall_sync, either we're already initialised, so do >> > > > return and nothing, or run through the entire flow, even if the TPM >> > > > isn't unavailable. >> > > > >> > > > So ima_init() just needs to know a) if it's in the sync or non-sync mode >> > > > and b) for the sync mode, if we've already done the init at >> > > > non-sync. >> > > >> > > Thanks, Jonathan. That is exactly what I'm suggesting. Any other changes >> > > should not be included in this patch. Since Yeoreum is not hearing me, feel >> > > free to post a patch. >> > >> > I see. so what you need to is this only >> > If it looks good to you. I'll send it at v3. >> >> FWIW, I pulled the tpm_default_chip check out a level to account for the >> extra init you mentioned, and have the following (completely untested or >> compiled, but gives the approach): > >Thanks, Jonathan! It looks good. Similarly untested/compiled. FWIW, it does compile. >Emitting a message on failure to initialize IMA at late_initcall is good, but >the attestation service won't know. Could you somehow differentiate between the >late_initcall and late_initcall_sync boot_aggregate records? Are you thinking "boot_aggregate" and "boot_aggregate_late" or similar as the "filename" on the entries, just so it's clear when we did the init in the log, or something else? J. -- /-\ | 101 things you can't have too much |@/ Debian GNU/Linux Developer | of : 39 - silver bullets. \- |