drm/vc4: Return -EFAULT on copy_from_user() failure

commit 585cb132 upstream.

The copy_from_user() function returns the number of bytes not copied but
we want to return a negative error code.

Fixes: 463873d5 ('drm/vc4: Add an API for creating GPU shaders in GEM BOs.')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/vc4/vc4_bo.c

@@ -499,11 +499,12 @@ vc4_create_shader_bo_ioctl(struct drm_device *dev, void *data,
 	if (IS_ERR(bo))
 		return PTR_ERR(bo);
 
-	ret = copy_from_user(bo->base.vaddr,
+	if (copy_from_user(bo->base.vaddr,
 			     (void __user *)(uintptr_t)args->data,
-			     args->size);
-	if (ret != 0)
+			     args->size)) {
+		ret = -EFAULT;
 		goto fail;
+	}
 	/* Clear the rest of the memory from allocating from the BO
 	 * cache.
 	 */