| Message ID | 20200201185218.24473-6-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: > 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>
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; }
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(-)