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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 7F60EC10F14 for ; Tue, 23 Apr 2019 11:06:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B06221738 for ; Tue, 23 Apr 2019 11:06:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727440AbfDWLGR (ORCPT ); Tue, 23 Apr 2019 07:06:17 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:33228 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726421AbfDWLGR (ORCPT ); Tue, 23 Apr 2019 07:06:17 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92 #3 (Red Hat Linux)) id 1hItFc-0005yi-Cj; Tue, 23 Apr 2019 11:06:12 +0000 Date: Tue, 23 Apr 2019 12:06:12 +0100 From: Al Viro To: "dmitry.torokhov@gmail.com" Cc: Mukesh Ojha , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Gaurav Kohli , Peter Hutterer , Martin Kepplinger , "Paul E. McKenney" Subject: Re: [PATCH v2] Input: uinput: Avoid Object-Already-Free with a global lock Message-ID: <20190423110611.GL2217@ZenIV.linux.org.uk> References: <1554883176-24318-1-git-send-email-mojha@codeaurora.org> <7299a6db-38b7-75c7-633a-00d2257eba45@codeaurora.org> <20190418014321.dptin7tpxpldhsns@penguin> <20190419071152.x5ghvbybjhv76uxt@penguin> <20190423032839.xvbldglrmjxkdntj@penguin> <17f4a0be-ab04-8537-9197-32fbca807f3f@codeaurora.org> <20190423084944.gj2boxfcg7lp4zad@penguin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190423084944.gj2boxfcg7lp4zad@penguin> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 23, 2019 at 08:49:44AM +0000, dmitry.torokhov@gmail.com wrote: > On Tue, Apr 23, 2019 at 12:51:13PM +0530, Mukesh Ojha wrote: > > I have taken care this case from ioctl and release point of view. > > > > Even if the release gets called first it will make the > > file->private_data=NULL. > > and further call to ioctl will not be a problem as the check is already > > there. > > Al, do we have any protections in VFS layer from userspace hanging onto > a file descriptor and calling ioctl() on it even as another thread > calls close() on the same fd? > > Should the issue be solved by individual drivers, or more careful > accounting for currently running operations is needed at VFS layer? Neither. An overlap of ->release() and ->ioctl() is possible only if you've got memory corruption somewhere. close() overlapping ioctl() is certainly possible, and won't trigger that at all - sys_ioctl() holds onto reference to struct file, so its refcount won't reach zero until we are done with it.