linux-kernel - Re: [PATCH v9 43/43] virt: sevguest: Add support to get extended report

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Date:   Mon, 7 Feb 2022 10:16:27 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v9 43/43] virt: sevguest: Add support to get extended
 report

On Fri, Jan 28, 2022 at 11:18:04AM -0600, Brijesh Singh wrote:
> +static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +{
> +	struct snp_guest_crypto *crypto = snp_dev->crypto;
> +	struct snp_ext_report_req req = {0};
> +	struct snp_report_resp *resp;
> +	int ret, npages = 0, resp_len;
> +
> +	if (!arg->req_data || !arg->resp_data)
> +		return -EINVAL;
> +
> +	/* Copy the request payload from userspace */

Useless comment.

> +	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> +		return -EFAULT;
> +
> +	if (req.certs_len) {
> +		if (req.certs_len > SEV_FW_BLOB_MAX_SIZE ||
> +		    !IS_ALIGNED(req.certs_len, PAGE_SIZE))
> +			return -EINVAL;
> +	}
> +
> +	if (req.certs_address && req.certs_len) {
> +		if (!access_ok(req.certs_address, req.certs_len))
> +			return -EFAULT;
> +
> +		/*
> +		 * Initialize the intermediate buffer with all zero's. This buffer

"zeros"

> +		 * is used in the guest request message to get the certs blob from
> +		 * the host. If host does not supply any certs in it, then copy
> +		 * zeros to indicate that certificate data was not provided.
> +		 */
> +		memset(snp_dev->certs_data, 0, req.certs_len);
> +
> +		npages = req.certs_len >> PAGE_SHIFT;
> +	}
> +
> +	/*
> +	 * The intermediate response buffer is used while decrypting the
> +	 * response payload. Make sure that it has enough space to cover the
> +	 * authtag.
> +	 */
> +	resp_len = sizeof(resp->data) + crypto->a_len;
> +	resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
> +	if (!resp)
> +		return -ENOMEM;
> +
> +	snp_dev->input.data_npages = npages;
> +	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
> +				   SNP_MSG_REPORT_REQ, &req.data,
> +				   sizeof(req.data), resp->data, resp_len, &arg->fw_err);
> +
> +	/* If certs length is invalid then copy the returned length */
> +	if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
> +		req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
> +
> +		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
> +			ret = -EFAULT;
> +	}
> +
> +	if (ret)
> +		goto e_free;
> +
> +	/* Copy the certificate data blob to userspace */
> +	if (req.certs_address && req.certs_len &&
> +	    copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
> +			 req.certs_len)) {
> +		ret = -EFAULT;
> +		goto e_free;
> +	}
> +
> +	/* Copy the response payload to userspace */

Both comments are not needed.

> +	if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> +		ret = -EFAULT;
> +
> +e_free:
> +	kfree(resp);
> +	return ret;
> +}

-- 
Regards/Gruss,
    Boris.

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