Re: [PATCH v20 7/9] arm64: Block hibernate and kexec while RMM is active

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] arm64: hibernation resume blind copy triggers GPF when RMM is active
--

commit cd33ba7dfabdc9882b5491e3f0d6693b247f8326
Author: Suzuki K Poulose <suzuki.poulose@arm.com>

arm64: Block hibernate and kexec while RMM is active

RMM can be deactivated only after all delegated granules have been
reclaimed. If a new kernel is entered while any granules remain in the
Realm PAS, accesses to that memory can raise a Granule Protection Fault
and be fatal to the new kernel.

> diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
> index 424291c547f02..253f544a59731 100644
> --- a/arch/arm64/kernel/hibernate.c
> +++ b/arch/arm64/kernel/hibernate.c

[ ... ]

> @@ -341,6 +342,11 @@ int swsusp_arch_suspend(void)
>  		return -EBUSY;
>  	}
>  
> +	if (is_rmm_active()) {
> +		pr_err("Can't hibernate: RMM is active.\n");
> +		return -EBUSY;
> +	}
> +

[Severity: High]
While this successfully prevents saving a hibernation image, is there a missing
check in the resume path, specifically arch_hibernation_header_restore() in
arch/arm64/kernel/hibernate.c?

If a hibernation image is present on disk (e.g., from a prior boot with RMM
disabled, but with a matching uts_version), subsys_initcall(arm64_init_rmi)
activates RMM and delegates memory to the Realm PAS early in boot.

Later, late_initcall_sync(software_resume_initcall) restores the image.
Because arch_hibernation_header_restore() lacks an is_rmm_active() check,
the image is accepted. The low-level resume path swsusp_arch_resume() then
blindly overwrites physical memory with the saved image.

Without an upstream guard during resume, won't this overwrite newly delegated
Realm PAS memory, triggering a fatal Granule Protection Fault?

>  	flags = local_daif_save();
>  
>  	if (__cpu_suspend_enter(&state)) {

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260929221623.1342076-1-suzuki.poulose@arm.com?part=7