build_mount_idmapped(): switch to fdget()

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -4197,7 +4197,7 @@ static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
 	int err = 0;
 	struct ns_common *ns;
 	struct user_namespace *mnt_userns;
-	struct file *file;
+	struct fd f;
 
 	if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
 		return 0;
@@ -4213,16 +4213,16 @@ static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
 	if (attr->userns_fd > INT_MAX)
 		return -EINVAL;
 
-	file = fget(attr->userns_fd);
-	if (!file)
+	f = fdget(attr->userns_fd);
+	if (!f.file)
 		return -EBADF;
 
-	if (!proc_ns_file(file)) {
+	if (!proc_ns_file(f.file)) {
 		err = -EINVAL;
 		goto out_fput;
 	}
 
-	ns = get_proc_ns(file_inode(file));
+	ns = get_proc_ns(file_inode(f.file));
 	if (ns->ops->type != CLONE_NEWUSER) {
 		err = -EINVAL;
 		goto out_fput;
@@ -4251,7 +4251,7 @@ static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
 	kattr->mnt_userns = get_user_ns(mnt_userns);
 
 out_fput:
-	fput(file);
+	fdput(f);
 	return err;
 }