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KVM: x86: Check userspace CPUID array size after validating sub-leaf

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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.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-03-02 15:56:08 -08:00 committed by Paolo Bonzini
parent d5a661d19d
commit 0fc6267187
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kvm/cpuid.c
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@ -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;
}