On 29/04/21 03:00, Sean Christopherson wrote:
On Wed, Apr 28, 2021, Valeriy Vdovin wrote:
It's very explicit by the code that it was designed to receive some
small number of entries to return E2BIG along with the corrected number.
LOL, saying KVM_GET_CPUID2 was "designed" is definitely giving the KVM
forefathers the benefit of the doubt.
I was going to make a different joke, i.e. that KVM_GET_CPUID2 was
indeed designed the way Valeriy described, but that design was forgotten
soon after.
Really, this ioctl has been such a trainwreck that I think the only good
solution here is to drop it.
Paolo
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index efc7a82ab140..3f941b1f4e78 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4773,14 +4773,17 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = -EFAULT;
if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
goto out;
+
r = kvm_vcpu_ioctl_get_cpuid2(vcpu, &cpuid,
cpuid_arg->entries);
- if (r)
+
+ if (r && r != -E2BIG)
goto out;
- r = -EFAULT;
- if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid)))
+
+ if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid))) {
+ r = -EFAULT;
goto out;
As I pointed out[*], copying the number of entries but not the entries themselves
is wrong. All of my feedback on v1 still stands.
[*] https://lkml.kernel.org/r/YIl4M/GgaYvwNuXv@xxxxxxxxxx
- r = 0;
+ }
break;
}
case KVM_GET_MSRS: {
