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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id w7sm3991741wmi.9.2020.02.06.07.24.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Feb 2020 07:24:49 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson Cc: Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH 05/61] KVM: x86: Check userapce CPUID array size after validating sub-leaf In-Reply-To: <20200201185218.24473-6-sean.j.christopherson@intel.com> References: <20200201185218.24473-1-sean.j.christopherson@intel.com> <20200201185218.24473-6-sean.j.christopherson@intel.com> Date: Thu, 06 Feb 2020 16:24:48 +0100 Message-ID: <87k14zg2m7.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sean Christopherson 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 > --- > 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 -- Vitaly