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. And the similar situation is reported on TPM devices attached on SPI bus[0]. To resolve this, introduce IMA_INIT_LATE_SYNC option to initialise IMA at late_inicall_sync so that IMA is initialized with the TPM device probed deffered. When this option is enabled, modules that access files in the initramfs through usermode helper calls such as request_module() during initcall must not be built-in. Otherwise, IMA may miss measuring those files since they're the file accesses before the initialisation of IMA [1]. Link: https://lore.kernel.org/all/[email protected]/ [0] Link: https://lore.kernel.org/all/[email protected]/ [1] Suggested-by: Mimi Zohar <[email protected]> Signed-off-by: Yeoreum Yun <[email protected]> --- security/integrity/ima/Kconfig | 10 ++++++++++ security/integrity/ima/ima_main.c | 4 ++++ 2 files changed, 14 insertions(+) diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig index 862fbee2b174..75f71401fba3 100644 --- a/security/integrity/ima/Kconfig +++ b/security/integrity/ima/Kconfig @@ -332,4 +332,14 @@ config IMA_KEXEC_EXTRA_MEMORY_KB If set to the default value of 0, an extra half page of memory for those additional measurements will be allocated. +config IMA_INIT_LATE_SYNC + bool "Initialise IMA at late_initcall_sync" + default n + help + This option initialises IMA at late_initcall_sync for platforms + where TPM device probing is deferred. + When this option is enabled, modules that access files in the + initramfs through usermode helper calls such as request_module() + during initcall must not be built-in. Otherwise, IMA may miss + file measurements for them. endif diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 5cea53fc36df..1cfae4b83dc5 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -1337,5 +1337,9 @@ DEFINE_LSM(ima) = { .order = LSM_ORDER_LAST, .blobs = &ima_blob_sizes, /* Start IMA after the TPM is available */ +#ifndef CONFIG_IMA_INIT_LATE_SYNC .initcall_late = init_ima, +#else + .initcall_late_sync = init_ima, +#endif }; -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
