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b=a9n1j7GTlWLZEaaJ12KTzLyos/ gAyuDeuM4gAiYt4D751cv6U2qGjExT33KlAwcQNOmKAa8j9ARjxzsSEMTowDcTzT9GatTfHVjgTIG COklNeeFQIToLy6KW0QQ084nvrTv5fAismMl9hS1/XChOC3HxXf0mUqDbPHdkkOwRor2/qJ5irBR+ heySi33NJLXvUrxqlbw6BIFY2jtFmnQ3Fyxu8kWaym3SWMwfZEjOQr4k+38x9d7Fxwf/HLKKRNeq7 COe2HP8WNj0HGkOoEjZ9YYvtMPsMpu9V6/vW1fiq0JvAxlGHSvUY5vr59PgSldnPv1ZFqmqv/mkM/ HQF+yMww==; Received: from noodles by the.earth.li with local (Exim 4.98.2) (envelope-from ) id 1wFudy-00000003Xf2-41TD; Thu, 23 Apr 2026 15:03:03 +0100 Date: Thu, 23 Apr 2026 15:03:02 +0100 From: Jonathan McDowell To: Yeoreum Yun Cc: Mimi Zohar , 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> 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: 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): diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index d48bf0ad26f4..88fe105b7f00 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -166,6 +166,7 @@ enum lsm_order { * @initcall_fs: LSM callback for fs_initcall setup, optional * @initcall_device: LSM callback for device_initcall() setup, optional * @initcall_late: LSM callback for late_initcall() setup, optional + * @initcall_late_sync: LSM callback for late_initcall_sync() setup, optional */ struct lsm_info { const struct lsm_id *id; @@ -181,6 +182,7 @@ struct lsm_info { int (*initcall_fs)(void); int (*initcall_device)(void); int (*initcall_late)(void); + int (*initcall_late_sync)(void); }; #define DEFINE_LSM(lsm) \ diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c index a2f34f2d8ad7..a60dfb8316d8 100644 --- a/security/integrity/ima/ima_init.c +++ b/security/integrity/ima/ima_init.c @@ -119,10 +119,6 @@ int __init ima_init(void) { int rc; - ima_tpm_chip = tpm_default_chip(); - if (!ima_tpm_chip) - pr_info("No TPM chip found, activating TPM-bypass!\n"); - rc = integrity_init_keyring(INTEGRITY_KEYRING_IMA); if (rc) return rc; diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 1d6229b156fb..b60a85fa803a 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -1237,7 +1237,7 @@ static int ima_kernel_module_request(char *kmod_name) #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */ -static int __init init_ima(void) +static int __init init_ima(bool sync) { int error; @@ -1247,6 +1247,19 @@ static int __init init_ima(void) return 0; } + /* If we found the TPM during our first attempt, nothing further to do */ + if (sync && ima_tpm_chip) + return 0; + + ima_tpm_chip = tpm_default_chip(); + if (!ima_tpm_chip && !sync) { + pr_debug("TPM not available, will try later\n"); + return -EPROBE_DEFER; + } + + if (!ima_tpm_chip) + pr_info("No TPM chip found, activating TPM-bypass!\n"); + ima_appraise_parse_cmdline(); ima_init_template_list(); hash_setup(CONFIG_IMA_DEFAULT_HASH); @@ -1274,6 +1287,16 @@ static int __init init_ima(void) return error; } +static int __init init_ima_late(void) +{ + return init_ima(false); +} + +static int __init init_ima_late_sync(void) +{ + return init_ima(true); +} + static struct security_hook_list ima_hooks[] __ro_after_init = { LSM_HOOK_INIT(bprm_check_security, ima_bprm_check), LSM_HOOK_INIT(bprm_creds_for_exec, ima_bprm_creds_for_exec), @@ -1319,6 +1342,7 @@ DEFINE_LSM(ima) = { .init = init_ima_lsm, .order = LSM_ORDER_LAST, .blobs = &ima_blob_sizes, - /* Start IMA after the TPM is available */ - .initcall_late = init_ima, + /* Ensure we start IMA after the TPM is available */ + .initcall_late = init_ima_late, + .initcall_late_sync = init_ima_late_sync, }; diff --git a/security/lsm_init.c b/security/lsm_init.c index 573e2a7250c4..4e5c59beb82a 100644 --- a/security/lsm_init.c +++ b/security/lsm_init.c @@ -547,13 +547,22 @@ device_initcall(security_initcall_device); * security_initcall_late - Run the LSM late initcalls */ static int __init security_initcall_late(void) +{ + return lsm_initcall(late); +} +late_initcall(security_initcall_late); + +/** + * security_initcall_late_sync - Run the LSM late initcalls sync + */ +static int __init security_initcall_late_sync(void) { int rc; - rc = lsm_initcall(late); + rc = lsm_initcall(late_sync); lsm_pr_dbg("all enabled LSMs fully activated\n"); call_blocking_lsm_notifier(LSM_STARTED_ALL, NULL); return rc; } -late_initcall(security_initcall_late); +late_initcall_sync(security_initcall_late_sync); J. -- Rock and roll stops the traffic. 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