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Fri, 05 Jun 2020 10:33:56 -0700 (PDT) Received: from [192.168.178.58] ([151.20.243.176]) by smtp.gmail.com with ESMTPSA id c16sm12977772wrx.4.2020.06.05.10.33.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Jun 2020 10:33:56 -0700 (PDT) Subject: Re: [PATCH v2 2/2] Revert "KVM: x86: work around leak of uninitialized stack contents" To: Vitaly Kuznetsov , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , linux-kernel@vger.kernel.org References: <20200605115906.532682-1-vkuznets@redhat.com> <20200605115906.532682-2-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: <100b82ab-d6f5-7b0e-2d4b-13bc16ec273f@redhat.com> Date: Fri, 5 Jun 2020 19:33:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200605115906.532682-2-vkuznets@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/06/20 13:59, Vitaly Kuznetsov wrote: > handle_vmptrst()/handle_vmread() stopped injecting #PF unconditionally > and switched to nested_vmx_handle_memory_failure() which just kills the > guest with KVM_EXIT_INTERNAL_ERROR in case of MMIO access, zeroing > 'exception' in kvm_write_guest_virt_system() is not needed anymore. > > This reverts commit 541ab2aeb28251bf7135c7961f3a6080eebcc705. > > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/kvm/x86.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 9e41b5135340..0097a97d331f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5647,13 +5647,6 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val, > /* kvm_write_guest_virt_system can pull in tons of pages. */ > vcpu->arch.l1tf_flush_l1d = true; > > - /* > - * FIXME: this should call handle_emulation_failure if X86EMUL_IO_NEEDED > - * is returned, but our callers are not ready for that and they blindly > - * call kvm_inject_page_fault. Ensure that they at least do not leak > - * uninitialized kernel stack memory into cr2 and error code. > - */ > - memset(exception, 0, sizeof(*exception)); > return kvm_write_guest_virt_helper(addr, val, bytes, vcpu, > PFERR_WRITE_MASK, exception); > } > Queued, thanks. Paolo