| Message ID | 20200201185218.24473-8-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Introduce KVM cpu caps | expand |
Sean Christopherson <sean.j.christopherson@intel.com> writes: > Now that sub-leaf 1 is handled separately, verify the next sub-leaf is > needed before rejecting KVM_GET_SUPPORTED_CPUID due to an insufficiently > sized 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 leaf 0xD. 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 | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index fc8540596386..fd9b29aa7abc 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -670,13 +670,14 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, > entry[1].edx = 0; > > for (idx = 2, i = 2; idx < 64; ++idx) { > - u64 mask = ((u64)1 << idx); > + if (!(supported & BIT_ULL(idx))) > + continue; > > if (*nent >= maxnent) > goto out; > > do_host_cpuid(&entry[i], function, idx); > - if (entry[i].eax == 0 || !(supported & mask)) > + if (entry[i].eax == 0) > continue; > if (WARN_ON_ONCE(entry[i].ecx & 1)) > continue; The remaining WARN_ON_ONCE() is technically the same 'bug not visible to userspace' :-) Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index fc8540596386..fd9b29aa7abc 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -670,13 +670,14 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, entry[1].edx = 0; for (idx = 2, i = 2; idx < 64; ++idx) { - u64 mask = ((u64)1 << idx); + if (!(supported & BIT_ULL(idx))) + continue; if (*nent >= maxnent) goto out; do_host_cpuid(&entry[i], function, idx); - if (entry[i].eax == 0 || !(supported & mask)) + if (entry[i].eax == 0) continue; if (WARN_ON_ONCE(entry[i].ecx & 1)) continue;
Now that sub-leaf 1 is handled separately, verify the next sub-leaf is needed before rejecting KVM_GET_SUPPORTED_CPUID due to an insufficiently sized 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 leaf 0xD. 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 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)