Commit ab322c43 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Update number of entries for KVM_GET_CPUID2 on success, not failure 



Update cpuid->nent if and only if kvm_vcpu_ioctl_get_cpuid2() succeeds.
The sole caller copies @cpuid to userspace only on success, i.e. the
existing code effectively does nothing.

Arguably, KVM should report the number of entries when returning -E2BIG so
that userspace doesn't have to guess the size, but all other similar KVM
ioctls() don't report the size either, i.e. userspace is conditioned to
guess.

Suggested-by: default avatarTakahiro Itazuri <itazur@amazon.com>
Link: https://lore.kernel.org/all/20230410141820.57328-1-itazur@amazon.com
Link: https://lore.kernel.org/r/20230526210340.2799158-2-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 0d42522b

arch/x86/kvm/cpuid.c

+4 −9
Original line number Diff line number Diff line
@@ -501,20 +501,15 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu, 
			      struct kvm_cpuid2 *cpuid,

			      struct kvm_cpuid_entry2 __user *entries)

{

	int r;



	r = -E2BIG;

	if (cpuid->nent < vcpu->arch.cpuid_nent)

		goto out;

	r = -EFAULT;

		return -E2BIG;



	if (copy_to_user(entries, vcpu->arch.cpuid_entries,

			 vcpu->arch.cpuid_nent * sizeof(struct kvm_cpuid_entry2)))

		goto out;

	return 0;

		return -EFAULT;



out:

	cpuid->nent = vcpu->arch.cpuid_nent;

	return r;

	return 0;

}



/* Mask kvm_cpu_caps for @leaf with the raw CPUID capabilities of this CPU. */