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,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 44020C433E0 for ; Sun, 17 May 2020 14:35:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B92720809 for ; Sun, 17 May 2020 14:35:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728021AbgEQOfo (ORCPT ); Sun, 17 May 2020 10:35:44 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59066 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727929AbgEQOfo (ORCPT ); Sun, 17 May 2020 10:35:44 -0400 Received: from ip5f5af183.dynamic.kabel-deutschland.de ([95.90.241.131] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jaKOE-0001QS-2z; Sun, 17 May 2020 14:35:42 +0000 Date: Sun, 17 May 2020 16:35:41 +0200 From: Christian Brauner To: Tycho Andersen Cc: Aleksa Sarai , Kees Cook , linux-api@vger.kernel.org, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] seccomp: Add group_leader pid to seccomp_notif Message-ID: <20200517143541.lh2mzuvcg7anobpc@wittgenstein> References: <20200515234005.32370-1-sargun@sargun.me> <202005162344.74A02C2D@keescook> <20200517104701.bbn2d2rqaplwchdw@wittgenstein> <20200517112156.cphs2h33hx2wfcs4@yavin.dot.cyphar.com> <20200517142316.GA1996744@cisco> <20200517143311.fmxaf3pnopuaezl4@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200517143311.fmxaf3pnopuaezl4@wittgenstein> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 17, 2020 at 04:33:11PM +0200, Christian Brauner wrote: > On Sun, May 17, 2020 at 08:23:16AM -0600, Tycho Andersen wrote: > > On Sun, May 17, 2020 at 09:21:56PM +1000, Aleksa Sarai wrote: > > > On 2020-05-17, Christian Brauner wrote: > > > > Or... And that's more invasive but ultimately cleaner we v2 the whole > > > > thing so e.g. SECCOMP_IOCTL_NOTIF_RECV2, SECCOMP_IOCTL_NOTIF_SEND2, and > > > > embedd the size argument in the structs. Userspace sets the size > > > > argument, we use get_user() to get the size first and then > > > > copy_struct_from_user() to handle it cleanly based on that. A similar > > > > model as with sched (has other unrelated quirks because they messed up > > > > something too): > > > > > > > > static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr) > > > > { > > > > u32 size; > > > > int ret; > > > > > > > > /* Zero the full structure, so that a short copy will be nice: */ > > > > memset(attr, 0, sizeof(*attr)); > > > > > > > > ret = get_user(size, &uattr->size); > > > > if (ret) > > > > return ret; > > > > > > > > /* ABI compatibility quirk: */ > > > > if (!size) > > > > size = SCHED_ATTR_SIZE_VER0; > > > > if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE) > > > > goto err_size; > > > > > > > > ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size); > > > > if (ret) { > > > > if (ret == -E2BIG) > > > > goto err_size; > > > > return ret; > > > > } > > > > > > > > We're probably the biggest user of this right now and I'd be ok with > > > > that change. If it's a v2 than whatever. :) > > > > > > I'm :+1: on a new version and switch to copy_struct_from_user(). I was a > > > little surprised when I found out that user_notif doesn't do it this > > > way a while ago (and although in theory it is userspace's fault, ideally > > > we could have an API that doesn't have built-in footguns). > > > > But I thought the whole point was that we couldn't do that, because > > there's two things that can vary in length (struct seccomp_notif and > > struct seccomp_data)? > > I may have missed that discussion you linked. > But why wouldn't: > > struct seccomp_notif2 { > __u32 notif_size; > __u64 id; > __u32 pid; > __u32 flags; > struct seccomp_data data; > __u32 data_size; > }; > > struct seccomp_notif_resp2 { > __u32 notif_resp_size; > __u64 id; > __s64 val; > __s32 error; > __u32 flags; > }; (Ignore the missing 32 bits here.)