On Fri, Aug 20, 2021 at 10:19:33AM -0500, Brijesh Singh wrote:

Version 2 of GHCB specification defines NAE to get the extended guest

Resolve "NAE" pls.

request. It is similar to the SNP_GET_REPORT ioctl. The main difference
is related to the additional data that be returned. The additional

"that will be returned"

"will contain"

+and snp_ext_report_req.certs_address will contains the certificate blob. If the

ditto.

+length of the blob is lesser than expected then snp_ext_report_req.certs_len will

"is smaller"

"from userspace"

+	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
+		return -EFAULT;
+
+	rreq = &req.data;
+
+	/* Message version must be non-zero */
+	if (!rreq->msg_version)
+		return -EINVAL;
+
+	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
+		 * 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 we copy

Please use passive voice: no "we" or "I", etc,

+		 * zeros to indicate that certificate data was not provided.
+		 */
+		memset(snp_dev->certs_data, 0, req.certs_len);
+
+		input.data_gpa = __pa(snp_dev->certs_data);
+		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;
+
+	if (copy_from_user(resp, (void __user *)arg->resp_data, sizeof(*resp))) {
+		ret = -EFAULT;
+		goto e_free;
+	}
+
+	/* Encrypt the userspace provided payload */
+	ret = enc_payload(snp_dev, rreq->msg_version, SNP_MSG_REPORT_REQ,
+			  &rreq->user_data, sizeof(rreq->user_data));
+	if (ret)
+		goto e_free;
+
+	/* Call firmware to process the request */
+	input.req_gpa = __pa(snp_dev->request);
+	input.resp_gpa = __pa(snp_dev->response);
+	input.data_npages = npages;
+	memset(snp_dev->response, 0, sizeof(*snp_dev->response));
+	ret = snp_issue_guest_request(EXT_GUEST_REQUEST, &input, &fw_err);
+
+	/* Popogate any firmware error to the userspace */
+	arg->fw_err = fw_err;
+
+	/* If certs length is invalid then copy the returned length */
+	if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
+		req.certs_len = input.data_npages << PAGE_SHIFT;
+
+		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
+			ret = -EFAULT;
+
+		goto e_free;
+	}
+
+	if (ret)
+		goto e_free;

This one is really confusing. You assign ret in the if branch
above but then you test ret outside too, just in case the
snp_issue_guest_request() call above has failed.

But then if that call has failed, you still go and do some cleanup work
for invalid certs length...

So that get_ext_report() function is doing too many things at once and
is crying to be split.

For example, the glue around snp_issue_guest_request() is already carved
out in handle_guest_request(). Why aren't you calling that function here
too?

That'll keep the enc, request, dec payload game separate and then the
rest of the logic can remain in get_ext_report()...

...

Same comments here as for patch 37.

+
 	misc = &snp_dev->misc;
 	misc->minor = MISC_DYNAMIC_MINOR;
 	misc->name = DEVICE_NAME;

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette