From 1893c9415ae8cad20da863c41bdf308e56a2dd67 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 2 Mar 2020 15:56:10 -0800 Subject: [PATCH] KVM: x86: Check for CPUID 0xD.N support before validating array size 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. Reviewed-by: Vitaly Kuznetsov Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- 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 fc85405..fd9b29a 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; -- 2.7.4