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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 1BB47C35641 for ; Fri, 21 Feb 2020 22:32:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED434206EF for ; Fri, 21 Feb 2020 22:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729195AbgBUWcV (ORCPT ); Fri, 21 Feb 2020 17:32:21 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:34104 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726802AbgBUWcV (ORCPT ); Fri, 21 Feb 2020 17:32:21 -0500 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id D6056295BD2; Fri, 21 Feb 2020 22:32:19 +0000 (GMT) Date: Fri, 21 Feb 2020 23:32:16 +0100 From: Boris Brezillon To: Vitor Soares Cc: linux-kernel@vger.kernel.org, linux-i3c@lists.infradead.org, Jose.Abreu@synopsys.com, corbet@lwn.net, Joao.Pinto@synopsys.com, arnd@arndb.de, wsa@the-dreams.de, gregkh@linuxfoundation.org, bbrezillon@kernel.org, broonie@kernel.org Subject: Re: [PATCH v3 4/5] i3c: add i3cdev module to expose i3c dev in /dev Message-ID: <20200221233216.3b2038f8@collabora.com> In-Reply-To: References: Organization: Collabora X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Feb 2020 01:20:42 +0100 Vitor Soares wrote: > +static int i3cdev_detach(struct device *dev, void *dummy) > +{ > + struct i3cdev_data *i3cdev; > + struct i3c_device *i3c; > + > + if (dev->type == &i3c_masterdev_type) > + return 0; > + > + i3c = dev_to_i3cdev(dev); > + > + i3cdev = i3cdev_get_drvdata(i3c); > + if (!i3cdev) > + return 0; > + > + /* Prevent transfers while cdev removal */ > + mutex_lock(&i3cdev->xfer_lock); > + cdev_del(&i3cdev->cdev); When cdev_del() returns there might be opened FDs pointing to your i3cdev [1] ... > + device_destroy(i3cdev_class, MKDEV(MAJOR(i3cdev_number), i3cdev->id)); > + mutex_unlock(&i3cdev->xfer_lock); > + > + ida_simple_remove(&i3cdev_ida, i3cdev->id); > + put_i3cdev(i3cdev); ... and you call put_i3cdev() here which frees the i3cdev object, leading to potential use-after-free if any of the fops (ioctl, read, write) are called on those dangling FDs. That's exactly the kind of nightmare I'd like to avoid. > + > + pr_debug("i3cdev: device [%s] unregistered\n", dev_name(&i3c->dev)); > + > + return 0; > +} > + [1]https://elixir.bootlin.com/linux/latest/source/fs/char_dev.c#L587