Re: [RFC Part2 PATCH v3 15/26] KVM: SVM: Add support for SEV LAUNCH_START command

[Brijesh Singh]

On 09/13/2017 12:25 PM, Borislav Petkov wrote:
...

> > +static void sev_deactivate_handle(struct kvm *kvm, int *error);
> > +static void sev_decommission_handle(struct kvm *kvm, int *error);
>
> Please move code in a way that you don't need those forward
> declarations. Also, I'm wondering if having all the SEV-related code
> could live in sev.c or so - svm.c is humongous.


Yes, svm.c is humongous.


...

> > +
> > +static void sev_decommission_handle(struct kvm *kvm, int *error)
> > +{
> > +	struct sev_data_decommission *data;
> > +
> > +	data = kzalloc(sizeof(*data), GFP_KERNEL);
>
> Also, better on stack. Please do that for the other functions below too.


Yes, some structures are small and I don't expect them to grow in newer API
spec. We should be able to move them on the stack. I will audit the code and
make the necessary changes.


....

> > +	ret = -EFAULT;
> > +	if (copy_from_user(&params, (void *)argp->data,
> > +				sizeof(struct kvm_sev_launch_start)))
>
> Sanity-check params. This is especially important if later we start
> using reserved fields.

Yes, I will add some upper bound check on the length field and add the
sanity-check just after copying the parameters from userspace


...

> > +		goto e_free;
> > +
> > +	ret = -ENOMEM;
> > +	start = kzalloc(sizeof(*start), GFP_KERNEL);
> > +	if (!start)
> > +		goto e_free;
> > +
> > +	/* Bit 15:6 reserved, must be 0 */
> > +	start->policy = params.policy & ~0xffc0;
> > +
> > +	if (params.dh_cert_length && params.dh_cert_address) {
>
> Yeah, we talked about this already: sanity-checking needed. But you get
> the idea.

Will do

...

>                  if (copy_from_user(session_addr,
> 				   (void *)params.session_address,
> 				   params.session_length))
>
> reads better to me. Better yet if you shorten those member names into
> s_addr and s_len and so on...

Will use your recommendation.

thanks