From 0fc62671876c29a80c16d41cbce782ff10795bef Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Mon, 2 Mar 2020 15:56:08 -0800 Subject: [PATCH] KVM: x86: Check userspace CPUID array size after validating sub-leaf 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 Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- 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; } -- 2.11.0