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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D427C6FD18 for ; Wed, 29 Mar 2023 20:51:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229674AbjC2UvC (ORCPT ); Wed, 29 Mar 2023 16:51:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229647AbjC2Uu7 (ORCPT ); Wed, 29 Mar 2023 16:50:59 -0400 Received: from mail-oa1-x35.google.com (mail-oa1-x35.google.com [IPv6:2001:4860:4864:20::35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4D1C4EC7 for ; Wed, 29 Mar 2023 13:50:58 -0700 (PDT) Received: by mail-oa1-x35.google.com with SMTP id 586e51a60fabf-17997ccf711so17647843fac.0 for ; Wed, 29 Mar 2023 13:50:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680123058; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=RKZ8GqIMOOJV+XfNmnVFARmYio/PItz2BJFiPWuDGSY=; b=fuwFruqEcX0EYq8qW6g2AP0E1DdtapZohNO+DyP5pc2AtlzNd+22EhRcbUCquzkJ3o 9ondMX7B4/3ZlXi7I1DArJceyY1jenpceRPefus+ASy+K2c7ia1aRS+3GzdLuDLHet1U F6iVGJEG/6ESVX7B6CewSuvp/TU0ln1xflg/CG0u1DtVzsJv4KXpUiAbewa/6jLmFtR7 93JhXLtQy9slp+aO4ZIZt/xVi4QHSC1FP06khiuaejykUfbuzanPPHtrNpN2clyhn0dA 2cUOWey18Xu74TMH3p2Lj7rAKAoiMWGv/hVjxs8TKjFO25Ldubc50fMD3E1uNFy/6puf xkSw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680123058; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=RKZ8GqIMOOJV+XfNmnVFARmYio/PItz2BJFiPWuDGSY=; b=MDAbKJCPauzSFpo29Kootow8vvDK5cIP0IPfKLmjxQup89gh4Ejxsr1/4dzB9VFvaH gT/69Ul5nVHfeKrdLhMlCZhGPVBfmxhS8MaWohHG51ZuEU+e4rv1W/lSNjUa26HRBisY CsHEwNasoKxiOqhdmfNmV/U+MjtLLRX8CKdPv0GOpr5ssoMBY8pQmaDMxavFyEue1Zo8 vkQLpRdp1rGBhBXJ6Zc+pLDptR0PfnGnKMjKSKMmsNo5IAHEuYCF5vaHJlAB/8PhI0OE tFQKiprnpnOTOlHvOpsUPZ31D9CNCl+mQjFKMyYNIcPdpm0iu5Wjb8PA6NcFClC/Xj2k WreQ== X-Gm-Message-State: AAQBX9e1bHdEK4kZGvT/QaLKyhgqwAjHWFLYRzc1cTwEUS5A48lPdXn+ 6ezqZu5syoMoWDfmbtDswLTEWeZxX8rtc4rS7PXQBg== X-Google-Smtp-Source: AKy350Y+kAtx1gY4HjjthjqP/HTIyk6FRS2h6MQd7ks70ztqf/xhYrlb+0Xf4oPw8b2Z8bGuN54EYWb9wk9wLqT0PE8= X-Received: by 2002:a05:6870:8897:b0:17e:6e31:9aa4 with SMTP id m23-20020a056870889700b0017e6e319aa4mr7972519oam.6.1680123057921; Wed, 29 Mar 2023 13:50:57 -0700 (PDT) MIME-Version: 1.0 References: <20230326092208.13613-1-laoar.shao@gmail.com> In-Reply-To: From: Stanislav Fomichev Date: Wed, 29 Mar 2023 13:50:45 -0700 Message-ID: Subject: Re: [RFC PATCH bpf-next 00/13] bpf: Introduce BPF namespace To: Yafang Shao Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Mar 28, 2023 at 8:03=E2=80=AFPM Yafang Shao = wrote: > > On Wed, Mar 29, 2023 at 1:15=E2=80=AFAM Stanislav Fomichev wrote: > > > > On 03/28, Yafang Shao wrote: > > > On Tue, Mar 28, 2023 at 1:28=E2=80=AFAM Stanislav Fomichev wrote: > > > > > > > > On 03/26, Yafang Shao wrote: > > > > > Currently only CAP_SYS_ADMIN can iterate BPF object IDs and conve= rt > > > IDs > > > > > to FDs, that's intended for BPF's security model[1]. Not only doe= s it > > > > > prevent non-privilidged users from getting other users' bpf progr= am, > > > but > > > > > also it prevents the user from iterating his own bpf objects. > > > > > > > > > In container environment, some users want to run bpf programs in = their > > > > > containers. These users can run their bpf programs under CAP_BPF = and > > > > > some other specific CAPs, but they can't inspect their bpf progra= ms > > > in a > > > > > generic way. For example, the bpftool can't be used as it require= s > > > > > CAP_SYS_ADMIN. That is very inconvenient. > > > > > > > > > Without CAP_SYS_ADMIN, the only way to get the information of a b= pf > > > object > > > > > which is not created by the process itself is with SCM_RIGHTS, th= at > > > > > requires each processes which created bpf object has to implement= a > > > unix > > > > > domain socket to share the fd of a bpf object between different > > > > > processes, that is really trivial and troublesome. > > > > > > > > > Hence we need a better mechanism to get bpf object info without > > > > > CAP_SYS_ADMIN. > > > > > > > > [..] > > > > > > > > > BPF namespace is introduced in this patchset with an attempt to r= emove > > > > > the CAP_SYS_ADMIN requirement. The user can create bpf map, prog = and > > > > > link in a specific bpf namespace, then these bpf objects will not= be > > > > > visible to the users in a different bpf namespace. But these bpf > > > > > objects are visible to its parent bpf namespace, so the sys admin= can > > > > > still iterate and inspect them. > > > > > > > > Does it essentially mean unpriv bpf? > > > > > Right. With CAP_BPF and some other CAPs enabled. > > > > > > Can I, as a non-root, create > > > > a new bpf namespace and start loading/attaching progs? > > > > > No, you can't create a new bpf namespace as a non-root, see also > > > copy_namespaces(). > > > In the container environment, new namespaces are always created by > > > containered, which is started by root. > > > > Are you talking about "if (!ns_capable(user_ns, CAP_SYS_ADMIN))" part > > from copy_namespaces? Isn't it trivially bypassed with a new user > > namespace? > > > > IIUC, I can create a new user namespace which gives me CAP_SYS_ADMIN > > in this particular user-ns. Then I can go on and create a new bpf > > namespace (with CAP_BPF) and go wild? I won't see anything from the > > other namespaces, but I'll be able to load/attach bpf programs? > > > > I don't think so. If you create a new userspace, and give the process > the CAP_BPF or CAP_SYS_ADMIN in this new user namespace but not the > initial namespace, you can't do that. Because currently only CAP_BPF > or CAP_SYS_ADMIN in the init user namespace can load/attach bpf > programs. > > > > > Maybe add a paragraph about now vs whatever you're proposing. > > > > > What I'm proposing in this patchset is to put bpf objects (map, prog, > > > link, and btf) into the bpf namespace. Next step I will put bpffs int= o > > > the bpf namespace as well. > > > That said, I'm trying to put all the objects created in bpf into the > > > bpf namespace. Below is a simple paragraph to illustrate it. > > > > > Regarding the unpriv user with CAP_BPF enabled, > > > Now | F= uture > > > ---------------------------------------------------------------------= --- > > > Iterate his BPF IDs | N | Y | > > > Iterate others' BPF IDs | N | N | > > > Convert his BPF IDs to FDs | N | Y | > > > Convert others' BPF IDs to FDs | N | N | > > > Get others' object info from pinned file | Y(*) | N | > > > ---------------------------------------------------------------------= --- > > > > > (*) It can be improved by, > > > 1). Different containers has different bpffs > > > 2). Setting file permission > > > That's not perfect, for example, if one single user has two bpf > > > instances, but we don't want them to inspect each other. > > > > I think the question here is what happens to the existing > > capable(CAP_BPF) checks? Do they become ns_capable(CAP_BPF) eventually? > > > > They won't become ns_capable(CAP_BPF). If it becomes > ns_capable(CAP_BPF), it will really go wild then. > > > And if not, I don't think it integrates well with the user namespaces? > > > > IIUC, it is the CAP_BPF which doesn't integrate with the user > namespaces, right? Yeah. And it's probably fine if we don't, I just wanted to see some explanation on the long-term plan. If the purpose is to have a bpf namespace and use it for pure isolation purposes, let's state it clearly in the cover letter. Otherwise it's not clear whether it's only about isolation or potentially allowing CAP_BPF in user namespaces. Maybe clone(CLONE_NEWBPF|CLONE_NEWUSER) should return an explicit error? (or maybe it already does, haven't looked at the patches) One other question I have is: should init bpf namespace see everything? Otherwise it might be hard to chase down the namespaces that loaded some BPF program... > -- > Regards > Yafang