Messages in this thread | | | Date | Mon, 24 Jan 2022 18:07:27 +0100 | Subject | Re: [PATCH 2/2] KVM: x86: Use memcmp in kvm_cpuid_check_equal() | From | Paolo Bonzini <> |
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On 1/24/22 17:52, Sean Christopherson wrote: > On Mon, Jan 24, 2022, Vitaly Kuznetsov wrote: >> Paolo Bonzini <pbonzini@redhat.com> writes: >>>> + if (memcmp(e2, vcpu->arch.cpuid_entries, nent * sizeof(*e2))) >>>> + return -EINVAL; >>> >>> Hmm, not sure about that due to the padding in struct kvm_cpuid_entry2. >>> It might break userspace that isn't too careful about zeroing it. > > Given that we already are fully committed to potentially breaking userspace by > disallowing KVM_SET_CPUID{2} after KVM_RUN, we might as well get greedy.
Hmm, I thought this series was because we were _not_ fully committed. :)
>> FWIW, QEMU zeroes the whole thing before setting individual CPUID >> entries. Legacy KVM_SET_CPUID call is also not afffected as it copies >> entries to a newly allocated "struct kvm_cpuid_entry2[]" and explicitly >> zeroes padding. >> >> Do we need to at least add a check for ".flags"? > > Yes.
Yes, we do. Alternatively, we can replace memdup with a copy in the style of KVM_CPUID.
Paolo
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