crypto: ccp: Use the stack and common buffer for status commands

Drop the dedicated status_cmd_buf and instead use a local variable for
PLATFORM_STATUS.  Now that the low level helper uses an internal buffer
for all commands, using the stack for the upper layers is safe even when
running with CONFIG_VMAP_STACK=y.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210406224952.4177376-7-seanjc@google.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

drivers/crypto/ccp/sev-dev.c

@@ -316,15 +316,14 @@ static int sev_platform_shutdown(int *error)
 
 static int sev_get_platform_state(int *state, int *error)
 {
-	struct sev_device *sev = psp_master->sev_data;
+	struct sev_user_data_status data;
 	int rc;
 
-	rc = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS,
-				 &sev->status_cmd_buf, error);
+	rc = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, &data, error);
 	if (rc)
 		return rc;
 
-	*state = sev->status_cmd_buf.state;
+	*state = data.state;
 	return rc;
 }
 
@@ -362,15 +361,14 @@ static int sev_ioctl_do_reset(struct sev_issue_cmd *argp, bool writable)
 
 static int sev_ioctl_do_platform_status(struct sev_issue_cmd *argp)
 {
-	struct sev_device *sev = psp_master->sev_data;
-	struct sev_user_data_status *data = &sev->status_cmd_buf;
+	struct sev_user_data_status data;
 	int ret;
 
-	ret = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, data, &argp->error);
+	ret = __sev_do_cmd_locked(SEV_CMD_PLATFORM_STATUS, &data, &argp->error);
 	if (ret)
 		return ret;
 
-	if (copy_to_user((void __user *)argp->data, data, sizeof(*data)))
+	if (copy_to_user((void __user *)argp->data, &data, sizeof(data)))
 		ret = -EFAULT;
 
 	return ret;
@@ -469,21 +467,20 @@ EXPORT_SYMBOL_GPL(psp_copy_user_blob);
 static int sev_get_api_version(void)
 {
 	struct sev_device *sev = psp_master->sev_data;
-	struct sev_user_data_status *status;
+	struct sev_user_data_status status;
 	int error = 0, ret;
 
-	status = &sev->status_cmd_buf;
-	ret = sev_platform_status(status, &error);
+	ret = sev_platform_status(&status, &error);
 	if (ret) {
 		dev_err(sev->dev,
 			"SEV: failed to get status. Error: %#x\n", error);
 		return 1;
 	}
 
-	sev->api_major = status->api_major;
-	sev->api_minor = status->api_minor;
-	sev->build = status->build;
-	sev->state = status->state;
+	sev->api_major = status.api_major;
+	sev->api_minor = status.api_minor;
+	sev->build = status.build;
+	sev->state = status.state;
 
 	return 0;
 }

drivers/crypto/ccp/sev-dev.h

@@ -46,7 +46,6 @@ struct sev_device {
 	unsigned int int_rcvd;
 	wait_queue_head_t int_queue;
 	struct sev_misc_dev *misc;
-	struct sev_user_data_status status_cmd_buf;
 	struct sev_data_init init_cmd_buf;
 
 	u8 api_major;