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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id z18sm3396225ejl.67.2021.10.22.00.14.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Oct 2021 00:14:09 -0700 (PDT) Message-ID: <419f25f5-41ef-1389-1103-3bbe4aa4ddd3@redhat.com> Date: Fri, 22 Oct 2021 09:14:08 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v3 7/8] nSVM: use vmcb_ctrl_area_cached instead of vmcb_control_area in struct svm_nested_state Content-Language: en-US To: Emanuele Giuseppe Esposito , kvm@vger.kernel.org Cc: Maxim Levitsky , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org References: <20211011143702.1786568-1-eesposit@redhat.com> <20211011143702.1786568-8-eesposit@redhat.com> From: Paolo Bonzini In-Reply-To: <20211011143702.1786568-8-eesposit@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/10/21 16:37, Emanuele Giuseppe Esposito wrote: > ZE)) > return -EFAULT; > - if (copy_to_user(&user_vmcb->control, &svm->nested.ctl, > + nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); > + if (copy_to_user(&user_vmcb->control, &ctl_temp, > sizeof(user_vmcb->control))) > return -EFAULT; This needs a memset of ctl_temp so that kernel memory contents are not leaked to userspace. However, it's also better to avoid large structs on the stack, and do a quick kzalloc/kfree instead: - nested_copy_vmcb_cache_to_control(&ctl_temp, &svm->nested.ctl); - if (copy_to_user(&user_vmcb->control, &ctl_temp, - sizeof(user_vmcb->control))) + + ctl = kzalloc(sizeof(*ctl), GFP_KERNEL); + if (!ctl) + return -ENOMEM; + nested_copy_vmcb_cache_to_control(ctl, &svm->nested.ctl); + r = copy_to_user(&user_vmcb->control, ctl, + sizeof(user_vmcb->control)); + kfree(ctl); + if (r) return -EFAULT; I can do this change when committing too. Paolo