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Message-ID: <79013520-363b-c180-4169-d77f4f493518@amd.com> Date: Thu, 14 Sep 2017 06:25:17 -0500 From: Brijesh Singh <brijesh.singh@....com> To: Borislav Petkov <bp@...e.de> Cc: brijesh.singh@....com, linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Joerg Roedel <joro@...tes.org>, "Michael S . Tsirkin" <mst@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>, \"Radim Krčmář\" <rkrcmar@...hat.com>, Tom Lendacky <thomas.lendacky@....com> Subject: Re: [RFC Part2 PATCH v3 19/26] KVM: svm: Add support for SEV GUEST_STATUS command On 9/14/17 5:35 AM, Borislav Petkov wrote: ... > + >> + if (copy_from_user(¶ms, (void *) argp->data, >> + sizeof(struct kvm_sev_guest_status))) > Let me try to understand what's going on here. You copy user data into > params... This is wrong -- since all the parameters in GET_STATUS is "OUT" hence we don't need to perform copy_from_user. I will fix it. thanks > >> + return -EFAULT; >> + >> + data = kzalloc(sizeof(*data), GFP_KERNEL); >> + if (!data) >> + return -ENOMEM; >> + >> + data->handle = sev_get_handle(kvm); >> + ret = sev_issue_cmd(kvm, SEV_CMD_GUEST_STATUS, data, &argp->error); >> + if (ret) >> + goto e_free; >> + >> + params.policy = data->policy; >> + params.state = data->state; >> + params.handle = data->handle; > ... *overwrite* the copied data which means, the copy meant *absolutely* > *nothing* at all! ... > > Also, why does userspace need to know the firmware ->handle? SEV firmware supports key-sharing, if guest policy allows sharing the key between VMs then we need the firmware->handle. If key-sharing feature is used then firmware->handle of the 1st VM will be passed into the LAUNCH_START of 2nd VM. I still have not coded up anything in qemu for key-sharing and also I am using GET_STATUS command in qemu yet. But wanted to make sure that if we decide to add "info sev-status" command in qemu-monitor to retrieve the SEV state information and then all the information is available to us.
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