On Mon, 2022-01-24 at 11:36 +0100, Vitaly Kuznetsov wrote:
> kvm_cpuid_check_equal() should also check .flags equality but instead
> of adding it to the existing check, just switch to using memcmp() for
> the whole 'struct kvm_cpuid_entry2'.
Is the struct padding guaranteed to be identical ?
>
> When .flags are not checked, kvm_cpuid_check_equal() may allow an update
> which it shouldn't but kvm_set_cpuid() does not actually update anything
> and just returns success.
>
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/kvm/cpuid.c | 13 ++-----------
> 1 file changed, 2 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 89d7822a8f5b..7dd9c8f4f46e 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -123,20 +123,11 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
> static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
> int nent)
> {
> - struct kvm_cpuid_entry2 *orig;
> - int i;
> -
> if (nent != vcpu->arch.cpuid_nent)
> return -EINVAL;
>
> - for (i = 0; i < nent; i++) {
> - orig = &vcpu->arch.cpuid_entries[i];
> - if (e2[i].function != orig->function ||
> - e2[i].index != orig->index ||
> - e2[i].eax != orig->eax || e2[i].ebx != orig->ebx ||
> - e2[i].ecx != orig->ecx || e2[i].edx != orig->edx)
> - return -EINVAL;
> - }
> + if (memcmp(e2, vcpu->arch.cpuid_entries, nent * sizeof(*e2)))
> + return -EINVAL;
>
> return 0;
> }
