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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id 5sm729450pfi.43.2021.04.28.18.00.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 18:00:10 -0700 (PDT) Date: Thu, 29 Apr 2021 01:00:06 +0000 From: Sean Christopherson To: Valeriy Vdovin Cc: linux-kernel@vger.kernel.org, Denis Lunev , Paolo Bonzini , Jonathan Corbet , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Shuah Khan , Aaron Lewis , Alexander Graf , Andrew Jones , Oliver Upton , Like Xu , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v4] KVM: x86: Fix KVM_GET_CPUID2 ioctl to return cpuid entries count Message-ID: References: <20210428172729.3551-1-valeriy.vdovin@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210428172729.3551-1-valeriy.vdovin@virtuozzo.com> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Apr 28, 2021, Valeriy Vdovin wrote: > It's very explicit by the code that it was designed to receive some > small number of entries to return E2BIG along with the corrected number. LOL, saying KVM_GET_CPUID2 was "designed" is definitely giving the KVM forefathers the benefit of the doubt. > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index efc7a82ab140..3f941b1f4e78 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4773,14 +4773,17 @@ long kvm_arch_vcpu_ioctl(struct file *filp, > r = -EFAULT; > if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid))) > goto out; > + > r = kvm_vcpu_ioctl_get_cpuid2(vcpu, &cpuid, > cpuid_arg->entries); > - if (r) > + > + if (r && r != -E2BIG) > goto out; > - r = -EFAULT; > - if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid))) > + > + if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid))) { > + r = -EFAULT; > goto out; As I pointed out[*], copying the number of entries but not the entries themselves is wrong. All of my feedback on v1 still stands. [*] https://lkml.kernel.org/r/YIl4M/GgaYvwNuXv@google.com > - r = 0; > + } > break; > } > case KVM_GET_MSRS: {