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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 C022AC433FE for ; Wed, 9 Dec 2020 01:58:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 802AE23A1D for ; Wed, 9 Dec 2020 01:58:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726254AbgLIB6L (ORCPT ); Tue, 8 Dec 2020 20:58:11 -0500 Received: from namei.org ([65.99.196.166]:59072 "EHLO mail.namei.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbgLIB6L (ORCPT ); Tue, 8 Dec 2020 20:58:11 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.namei.org (Postfix) with ESMTPS id 0430BDC0; Wed, 9 Dec 2020 01:57:30 +0000 (UTC) Date: Tue, 8 Dec 2020 17:57:29 -0800 (PST) From: James Morris To: Miklos Szeredi cc: "Eric W . Biederman" , linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Vyukov Subject: Re: [PATCH v2 04/10] ovl: make ioctl() safe In-Reply-To: <20201207163255.564116-5-mszeredi@redhat.com> Message-ID: References: <20201207163255.564116-1-mszeredi@redhat.com> <20201207163255.564116-5-mszeredi@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 7 Dec 2020, Miklos Szeredi wrote: > ovl_ioctl_set_flags() does a capability check using flags, but then the > real ioctl double-fetches flags and uses potentially different value. > > The "Check the capability before cred override" comment misleading: user > can skip this check by presenting benign flags first and then overwriting > them to non-benign flags. Is this a security bug which should be fixed in stable? -- James Morris