Re: [PATCH v6 07/12] x86/cpu/keylocker: Load an internal wrapping key at boot-time

[Chang S. Bae]

On 5/8/2023 12:18 PM, Elliott, Robert (Servers) wrote:
> > diff --git a/arch/x86/kernel/keylocker.c b/arch/x86/kernel/keylocker.c
> ...
> > +void __init destroy_keylocker_data(void)
> > +{
> > +     memset(&kl_setup.key, KEY_DESTROY, sizeof(kl_setup.key));
> > +}
>
> That's a special value for garbage collected keyring keys assigned
> a keytype of ".dead". memzero() or memzero_explicit() might be better
> for this use case.
memzero() looks to be the same as memset() in x86:

$ git grep memzero arch/x86/ | grep define
arch/x86/boot/compressed/misc.c:#define memzero(s, n)   memset((s), 0, (n))

Instead, memzero_explicit() looks to be about the right call here:

/**
 * memzero_explicit - Fill a region of memory (e.g. sensitive
 *		      keying data) with 0s.
 ...
 * Note: usually using memset() is just fine (!), but in cases
 * where clearing out _local_ data at the end of a scope is
 * necessary, memzero_explicit() should be used instead in
 * order to prevent the compiler from optimising away zeroing.
 ...

Then,

void __init destroy_keylocker_data(void)
{
	memzero_explicit(&kl_setup.key, sizeof(kl_setup.key));
}

Thanks,
Chang