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SubjectRe: [PATCH 05/61] KVM: x86: Check userapce CPUID array size after validating sub-leaf
Date
Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Verify that the next sub-leaf of CPUID 0x4 (or 0x8000001d) is valid
> before rejecting the entire KVM_GET_SUPPORTED_CPUID due to insufficent
> space in the userspace array.
>
> Note, although this is technically a bug, it's not visible to userspace
> as KVM_GET_SUPPORTED_CPUID is guaranteed to fail on KVM_CPUID_SIGNATURE,
> which is hardcoded to be added after the affected leafs. The real
> motivation for the change is to tightly couple the nent/maxnent and
> do_host_cpuid() sequences in preparation for future cleanup.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/cpuid.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 11d5f311ef10..e5cf1e0cf84a 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -552,12 +552,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
>
> /* read more entries until cache_type is zero */
> for (i = 1; ; ++i) {
> - if (*nent >= maxnent)
> - goto out;
> -
> cache_type = entry[i - 1].eax & 0x1f;
> if (!cache_type)
> break;
> +
> + if (*nent >= maxnent)
> + goto out;
> do_host_cpuid(&entry[i], function, i);
> ++*nent;
> }

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly

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