[PATCH v2 1/9] KVM: PPC: Book3S HV: Fix H_REGISTER_VPA VPA size validation

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:

> KVM currently validates the size of the VPA registered by the client
> against sizeof(struct lppaca), however we align (and therefore size)
> that struct to 1kB to avoid crossing a 4kB boundary in the client.
>
> PAPR calls for sizes >= 640 bytes to be accepted. Hard code this with
> a comment.
>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>  arch/powerpc/kvm/book3s_hv.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)

This one should go via Paul.

Hopefully he can just pick it up.

cheers

> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 359c79cdf0cc..1182cfd79857 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -485,7 +485,13 @@ static unsigned long do_h_register_vpa(struct kvm_vcpu *vcpu,
>  
>  	switch (subfunc) {
>  	case H_VPA_REG_VPA:		/* register VPA */
> -		if (len < sizeof(struct lppaca))
> +		/*
> +		 * The size of our lppaca is 1kB because of the way we align
> +		 * it for the guest to avoid crossing a 4kB boundary. We only
> +		 * use 640 bytes of the structure though, so we should accept
> +		 * clients that set a size of 640.
> +		 */
> +		if (len < 640)
>  			break;
>  		vpap = &tvcpu->arch.vpa;
>  		err = 0;
> -- 
> 2.13.3