drm/i915: use memdup_user_nul

Use memdup_user_nul() helper instead of open-coding to simplify the
code.
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/6baf3aa45d0b5e0fd016b508bac905ebf8443aac.1493779294.git.geliangtang@gmail.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -3702,16 +3702,10 @@ static ssize_t i915_displayport_test_active_write(struct file *file,
 	if (len == 0)
 		return 0;
 
-	input_buffer = kmalloc(len + 1, GFP_KERNEL);
-	if (!input_buffer)
-		return -ENOMEM;
+	input_buffer = memdup_user_nul(ubuf, len);
+	if (IS_ERR(input_buffer))
+		return PTR_ERR(input_buffer);
 
-	if (copy_from_user(input_buffer, ubuf, len)) {
-		status = -EFAULT;
-		goto out;
-	}
-
-	input_buffer[len] = '\0';
 	DRM_DEBUG_DRIVER("Copied %d bytes from user\n", (unsigned int)len);
 
 	drm_connector_list_iter_begin(dev, &conn_iter);
@@ -3737,7 +3731,6 @@ static ssize_t i915_displayport_test_active_write(struct file *file,
 		}
 	}
 	drm_connector_list_iter_end(&conn_iter);
-out:
 	kfree(input_buffer);
 	if (status < 0)
 		return status;

drivers/gpu/drm/i915/intel_pipe_crc.c

@@ -853,19 +853,12 @@ static ssize_t display_crc_ctl_write(struct file *file, const char __user *ubuf,
 		return -E2BIG;
 	}
 
-	tmpbuf = kmalloc(len + 1, GFP_KERNEL);
-	if (!tmpbuf)
-		return -ENOMEM;
-
-	if (copy_from_user(tmpbuf, ubuf, len)) {
-		ret = -EFAULT;
-		goto out;
-	}
-	tmpbuf[len] = '\0';
+	tmpbuf = memdup_user_nul(ubuf, len);
+	if (IS_ERR(tmpbuf))
+		return PTR_ERR(tmpbuf);
 
 	ret = display_crc_ctl_parse(dev_priv, tmpbuf, len);
 
-out:
 	kfree(tmpbuf);
 	if (ret < 0)
 		return ret;