6.15-stable review patch. If anyone has any objections, please let me know.
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From: Yeoreum Yun yeoreum.yun@arm.com
[ Upstream commit 0e0546eabcd6c19765a8dbf5b5db3723e7b0ea75 ]
The Linux IMA (Integrity Measurement Architecture) subsystem used for secure boot, file integrity, or remote attestation cannot be a loadable module for few reasons listed below:
o Boot-Time Integrity: IMA’s main role is to measure and appraise files before they are used. This includes measuring critical system files during early boot (e.g., init, init scripts, login binaries). If IMA were a module, it would be loaded too late to cover those.
o TPM Dependency: IMA integrates tightly with the TPM to record measurements into PCRs. The TPM must be initialized early (ideally before init_ima()), which aligns with IMA being built-in.
o Security Model: IMA is part of a Trusted Computing Base (TCB). Making it a module would weaken the security model, as a potentially compromised system could delay or tamper with its initialization.
IMA must be built-in to ensure it starts measuring from the earliest possible point in boot which inturn implies TPM must be initialised and ready to use before IMA.
To enable integration of tpm_event_log with the IMA subsystem, the TPM drivers (tpm_crb and tpm_crb_ffa) also needs to be built-in. However with FF-A driver also being initialised at device initcall level, it can lead to an initialization order issue where: - crb_acpi_driver_init() may run before tpm_crb_ffa_driver()_init and ffa_init() - As a result, probing the TPM device via CRB over FFA is deferred - ima_init() (called as a late initcall) runs before deferred probe completes, IMA fails to find the TPM and logs the below error:
| ima: No TPM chip found, activating TPM-bypass!
Eventually it fails to generate boot_aggregate with PCR values.
Because of the above stated dependency, the ffa driver needs to initialised before tpm_crb_ffa module to ensure IMA finds the TPM successfully when present.
[ jarkko: reformatted some of the paragraphs because they were going past the 75 character boundary. ]
Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com Reviewed-by: Mimi Zohar zohar@linux.ibm.com Reviewed-by: Sudeep Holla sudeep.holla@arm.com Reviewed-by: Jarkko Sakkinen jarkko@kernel.org Signed-off-by: Jarkko Sakkinen jarkko@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/arm_ffa/driver.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c index 37eb2e6c2f9f..65bf1685350a 100644 --- a/drivers/firmware/arm_ffa/driver.c +++ b/drivers/firmware/arm_ffa/driver.c @@ -2059,7 +2059,7 @@ static int __init ffa_init(void) kfree(drv_info); return ret; } -module_init(ffa_init); +rootfs_initcall(ffa_init);
static void __exit ffa_exit(void) {