From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E2817C47247 for ; Thu, 7 May 2020 23:31:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C203521655 for ; Thu, 7 May 2020 23:31:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726742AbgEGXbh (ORCPT ); Thu, 7 May 2020 19:31:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726445AbgEGXbg (ORCPT ); Thu, 7 May 2020 19:31:36 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A10CC05BD43; Thu, 7 May 2020 16:31:36 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWpzI-003Ikq-FG; Thu, 07 May 2020 23:31:32 +0000 Date: Fri, 8 May 2020 00:31:32 +0100 From: Al Viro To: Jens Axboe Cc: Max Kellermann , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] fs/io_uring: fix O_PATH fds in openat, openat2, statx Message-ID: <20200507233132.GJ23230@ZenIV.linux.org.uk> References: <20200507185725.15840-1-mk@cm4all.com> <20200507190131.GF23230@ZenIV.linux.org.uk> <4cac0e53-656c-50f0-3766-ae3cc6c0310a@kernel.dk> <20200507192903.GG23230@ZenIV.linux.org.uk> <8e3c88cc-027b-4f90-b4f8-a20d11d35c4b@kernel.dk> <20200507220637.GH23230@ZenIV.linux.org.uk> <283c8edb-fea2-5192-f1d6-3cc57815b1e2@kernel.dk> <20200507224447.GI23230@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 07, 2020 at 05:03:17PM -0600, Jens Axboe wrote: > On 5/7/20 4:44 PM, Al Viro wrote: > > On Thu, May 07, 2020 at 04:25:24PM -0600, Jens Axboe wrote: > > > >> static int io_close(struct io_kiocb *req, bool force_nonblock) > >> { > >> + struct files_struct *files = current->files; > >> int ret; > >> > >> req->close.put_file = NULL; > >> - ret = __close_fd_get_file(req->close.fd, &req->close.put_file); > >> + spin_lock(&files->file_lock); > >> + if (req->file->f_op == &io_uring_fops || > >> + req->close.fd == req->ctx->ring_fd) { > >> + spin_unlock(&files->file_lock); > >> + return -EBADF; > >> + } > >> + > >> + ret = __close_fd_get_file_locked(files, req->close.fd, > >> + &req->close.put_file); > > > > Pointless. By that point req->file might have nothing in common with > > anything in any descriptor table. > > How about the below then? Stop using req->file, defer the lookup until > we're in the handler instead. Not sure the 'fd' check makes sense > at this point, but at least we should be consistent in terms of > once we lookup the file and check the f_op. Actually, what _is_ the reason for that check? Note, BTW, that if the file in question happens to be an AF_UNIX socket, closing it will close all references held in SCM_RIGHTS datagrams sitting in its queue, which might very well include io_uring files. IOW, if tries to avoid something really unpleasant, it's not enough. And if it doesn't, then what is it for?