1 files changed, 122 insertions, 69 deletions

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 7b4e9009f335..97dbe715e96a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -31,6 +31,9 @@
 #define AAD_LEN		48
 #define MSG_HDR_VER	1
 
+#define SNP_REQ_MAX_RETRY_DURATION	(60*HZ)
+#define SNP_REQ_RETRY_DELAY		(2*HZ)
+
 struct snp_guest_crypto {
 	struct crypto_aead *tfm;
 	u8 *iv, *authtag;
@@ -43,7 +46,15 @@ struct snp_guest_dev {
 
 	void *certs_data;
 	struct snp_guest_crypto *crypto;
+	/* request and response are in unencrypted memory */
 	struct snp_guest_msg *request, *response;
+
+	/*
+	 * Avoid information leakage by double-buffering shared messages
+	 * in fields that are in regular encrypted memory.
+	 */
+	struct snp_guest_msg secret_request, secret_response;
+
 	struct snp_secrets_page_layout *layout;
 	struct snp_req_data input;
 	u32 *os_area_msg_seqno;
@@ -263,14 +274,17 @@ static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
 static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
 {
 	struct snp_guest_crypto *crypto = snp_dev->crypto;
-	struct snp_guest_msg *resp = snp_dev->response;
-	struct snp_guest_msg *req = snp_dev->request;
+	struct snp_guest_msg *resp = &snp_dev->secret_response;
+	struct snp_guest_msg *req = &snp_dev->secret_request;
 	struct snp_guest_msg_hdr *req_hdr = &req->hdr;
 	struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
 
 	dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
 		resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
 
+	/* Copy response from shared memory to encrypted memory. */
+	memcpy(resp, snp_dev->response, sizeof(*resp));
+
 	/* Verify that the sequence counter is incremented by 1 */
 	if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
 		return -EBADMSG;
@@ -294,7 +308,7 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
 static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
 			void *payload, size_t sz)
 {
-	struct snp_guest_msg *req = snp_dev->request;
+	struct snp_guest_msg *req = &snp_dev->secret_request;
 	struct snp_guest_msg_hdr *hdr = &req->hdr;
 
 	memset(req, 0, sizeof(*req));
@@ -318,45 +332,40 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	return __enc_payload(snp_dev, req, payload, sz);
 }
 
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
-				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
-				u32 resp_sz, __u64 *fw_err)
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
+				  struct snp_guest_request_ioctl *rio)
 {
-	unsigned long err;
-	u64 seqno;
+	unsigned long req_start = jiffies;
+	unsigned int override_npages = 0;
+	u64 override_err = 0;
 	int rc;
 
-	/* Get message sequence and verify that its a non-zero */
-	seqno = snp_get_msg_seqno(snp_dev);
-	if (!seqno)
-		return -EIO;
-
-	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
-
-	/* Encrypt the userspace provided payload */
-	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
-	if (rc)
-		return rc;
-
+retry_request:
 	/*
 	 * Call firmware to process the request. In this function the encrypted
 	 * message enters shared memory with the host. So after this call the
 	 * sequence number must be incremented or the VMPCK must be deleted to
 	 * prevent reuse of the IV.
 	 */
-	rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
-
-	/*
-	 * If the extended guest request fails due to having too small of a
-	 * certificate data buffer, retry the same guest request without the
-	 * extended data request in order to increment the sequence number
-	 * and thus avoid IV reuse.
-	 */
-	if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
-	    err == SNP_GUEST_REQ_INVALID_LEN) {
-		const unsigned int certs_npages = snp_dev->input.data_npages;
+	rc = snp_issue_guest_request(exit_code, &snp_dev->input, rio);
+	switch (rc) {
+	case -ENOSPC:
+		/*
+		 * If the extended guest request fails due to having too
+		 * small of a certificate data buffer, retry the same
+		 * guest request without the extended data request in
+		 * order to increment the sequence number and thus avoid
+		 * IV reuse.
+		 */
+		override_npages = snp_dev->input.data_npages;
+		exit_code	= SVM_VMGEXIT_GUEST_REQUEST;
 
-		exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+		/*
+		 * Override the error to inform callers the given extended
+		 * request buffer size was too small and give the caller the
+		 * required buffer size.
+		 */
+		override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN);
 
 		/*
 		 * If this call to the firmware succeeds, the sequence number can
@@ -366,15 +375,20 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		 * of the VMPCK and the error code being propagated back to the
 		 * user as an ioctl() return code.
 		 */
-		rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+		goto retry_request;
 
-		/*
-		 * Override the error to inform callers the given extended
-		 * request buffer size was too small and give the caller the
-		 * required buffer size.
-		 */
-		err = SNP_GUEST_REQ_INVALID_LEN;
-		snp_dev->input.data_npages = certs_npages;
+	/*
+	 * The host may return SNP_GUEST_VMM_ERR_BUSY if the request has been
+	 * throttled. Retry in the driver to avoid returning and reusing the
+	 * message sequence number on a different message.
+	 */
+	case -EAGAIN:
+		if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
+			rc = -ETIMEDOUT;
+			break;
+		}
+		schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
+		goto retry_request;
 	}
 
 	/*
@@ -385,38 +399,75 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 */
 	snp_inc_msg_seqno(snp_dev);
 
-	if (fw_err)
-		*fw_err = err;
+	if (override_err) {
+		rio->exitinfo2 = override_err;
+
+		/*
+		 * If an extended guest request was issued and the supplied certificate
+		 * buffer was not large enough, a standard guest request was issued to
+		 * prevent IV reuse. If the standard request was successful, return -EIO
+		 * back to the caller as would have originally been returned.
+		 */
+		if (!rc && override_err == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
+			rc = -EIO;
+	}
+
+	if (override_npages)
+		snp_dev->input.data_npages = override_npages;
+
+	return rc;
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
+				struct snp_guest_request_ioctl *rio, u8 type,
+				void *req_buf, size_t req_sz, void *resp_buf,
+				u32 resp_sz)
+{
+	u64 seqno;
+	int rc;
+
+	/* Get message sequence and verify that its a non-zero */
+	seqno = snp_get_msg_seqno(snp_dev);
+	if (!seqno)
+		return -EIO;
+
+	/* Clear shared memory's response for the host to populate. */
+	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+	/* Encrypt the userspace provided payload in snp_dev->secret_request. */
+	rc = enc_payload(snp_dev, seqno, rio->msg_version, type, req_buf, req_sz);
+	if (rc)
+		return rc;
 
 	/*
-	 * If an extended guest request was issued and the supplied certificate
-	 * buffer was not large enough, a standard guest request was issued to
-	 * prevent IV reuse. If the standard request was successful, return -EIO
-	 * back to the caller as would have originally been returned.
+	 * Write the fully encrypted request to the shared unencrypted
+	 * request page.
 	 */
-	if (!rc && err == SNP_GUEST_REQ_INVALID_LEN)
-		return -EIO;
+	memcpy(snp_dev->request, &snp_dev->secret_request,
+	       sizeof(snp_dev->secret_request));
 
+	rc = __handle_guest_request(snp_dev, exit_code, rio);
 	if (rc) {
+		if (rc == -EIO &&
+		    rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
+			return rc;
+
 		dev_alert(snp_dev->dev,
-			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
-			  rc, *fw_err);
-		goto disable_vmpck;
+			  "Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
+			  rc, rio->exitinfo2);
+
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
 	if (rc) {
-		dev_alert(snp_dev->dev,
-			  "Detected unexpected decode failure from ASP. rc: %d\n",
-			  rc);
-		goto disable_vmpck;
+		dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	return 0;
-
-disable_vmpck:
-	snp_disable_vmpck(snp_dev);
-	return rc;
 }
 
 static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
@@ -444,9 +495,9 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 	if (!resp)
 		return -ENOMEM;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
 				  SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
-				  resp_len, &arg->fw_err);
+				  resp_len);
 	if (rc)
 		goto e_free;
 
@@ -484,9 +535,8 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
 	if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
 		return -EFAULT;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
-				  SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len,
-				  &arg->fw_err);
+	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
+				  SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len);
 	if (rc)
 		return rc;
 
@@ -546,12 +596,12 @@ cmd:
 		return -ENOMEM;
 
 	snp_dev->input.data_npages = npages;
-	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
+	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg,
 				   SNP_MSG_REPORT_REQ, &req.data,
-				   sizeof(req.data), resp->data, resp_len, &arg->fw_err);
+				   sizeof(req.data), resp->data, resp_len);
 
 	/* If certs length is invalid then copy the returned length */
-	if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
+	if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
 		req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
 
 		if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
@@ -586,7 +636,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
 	if (copy_from_user(&input, argp, sizeof(input)))
 		return -EFAULT;
 
-	input.fw_err = 0xff;
+	input.exitinfo2 = 0xff;
 
 	/* Message version must be non-zero */
 	if (!input.msg_version)
@@ -617,7 +667,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
 
 	mutex_unlock(&snp_cmd_mutex);
 
-	if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
+	if (input.exitinfo2 && copy_to_user(argp, &input, sizeof(input)))
 		return -EFAULT;
 
 	return ret;
@@ -703,6 +753,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	void __iomem *mapping;
 	int ret;
 
+	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+		return -ENODEV;
+
 	if (!dev->platform_data)
 		return -ENODEV;