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@google.com
r = 0;
}