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 defered. 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] Patch history ============= from v3 to v4: - rebase on v7.1-rc5 - introduce IMA_INIT_LATE_SYNC option to control IMA initailisation. - https://lore.kernel.org/all/[email protected]/ from v2 to v3: - Drop ff-a/pKVM diff (this seems to have a separate set of discussion) - Rework IMA delayed initialisation to avoid delaying when unnecessary - Ensure IMA log clearly indicates when we've initialised late - https://lore.kernel.org/all/[email protected]/ from v1 to v2: - add notifier to make ffa-driver pkvm initialised. - modify to try initailisation again when IMA coudln't find proper TPM device. - https://lore.kernel.org/all/[email protected]/#t Yeoreum Yun (3): security: lsm: Allow LSMs to register for late_initcall_sync init security: ima: introduce IMA_INIT_LATE_SYNC option tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in drivers/char/tpm/tpm_crb_ffa.c | 18 +++--------------- include/linux/lsm_hooks.h | 2 ++ security/integrity/ima/Kconfig | 10 ++++++++++ security/integrity/ima/ima_main.c | 4 ++++ security/lsm_init.c | 13 +++++++++++-- 5 files changed, 30 insertions(+), 17 deletions(-) base-commit: e7ae89a0c97ce2b68b0983cd01eda67cf373517d -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
