From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga07-in.huawei.com (szxga07-in.huawei.com [45.249.212.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3BB0163C; Thu, 15 Aug 2024 00:50:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.35 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723683031; cv=none; b=X1V6g4LwzEDyVCRPj/VH5NdsKtd4Gjtx5g8DMX4//rh1j9MASGNNSeYPhNeTwb7MINHyoN6Yb6mqR7aZsL7+LV4nQqz21/S0deOfOACEJrcCbu0F8OnqmDHUXqTtvxYFkh8DCXhdo3dJmr7sL6J8oP/7Oms/mJi8otxVXAr/AWI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723683031; c=relaxed/simple; bh=Ij4+QPPx2+AHdCXlWTY6O7Em3IWid+VZPTixUOq+CDc=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=XfcuDjn+ALxX9LdHQrL0Z53U9+5S1yXp+HUzMD6JeKnHP0ZF4KOVNARFChfQtnC3bPOqYYM0dv1zpTwbJIRxVP/N3OYSMLZmfkx7JivquYciW5fhhPnPpacaIojJMYRTJ4b19KrX8E7rOv52qF29nioEMqVXsyd3TA98e4UsAc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.35 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.44]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4Wkmcr5GXrz1S7vK; Thu, 15 Aug 2024 08:45:32 +0800 (CST) Received: from kwepemd100013.china.huawei.com (unknown [7.221.188.163]) by mail.maildlp.com (Postfix) with ESMTPS id CAEEA1400DC; Thu, 15 Aug 2024 08:50:25 +0800 (CST) Received: from [10.67.109.79] (10.67.109.79) by kwepemd100013.china.huawei.com (7.221.188.163) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Thu, 15 Aug 2024 08:50:25 +0800 Message-ID: Date: Thu, 15 Aug 2024 08:50:24 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next 2/2] cgroup: Disallow delegatee to write all interfaces outsize of cgroup ns To: Tejun Heo CC: =?UTF-8?Q?Michal_Koutn=C3=BD?= , , , , , References: <20240812073746.3070616-1-chenridong@huawei.com> <20240812073746.3070616-3-chenridong@huawei.com> Content-Language: en-US From: chenridong In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemd100013.china.huawei.com (7.221.188.163) On 2024/8/15 0:52, Tejun Heo wrote: > Hello, > > On Wed, Aug 14, 2024 at 04:09:59PM +0800, chenridong wrote: > ... >> Hi，TJ， We plan to use delegation in cgroup-v2, so I am conducting some >> tests. >> As doc mentions 'Because the resource control interface files in a given >> directory control the distribution of the parent's resources, the delegatee >> shouldn't be allowed to write to them.' However I found a root can write >> parent's file(cgroup.subtree_control) to change the resource limits(a >> fraudulent method). I believe this could pose a risk in some scenarios where >> a root enters a new cgroup ns without unmounting original cgroup system, and >> it can break limitations. For instance, running a docker with --privileged, >> could this be a risk? >> >> So I sent this patch to discuss whether this case should be addressed? > > That sounsd like a misconfiguration. cgroup NS doesn't make much sense if > you don't limit the actual visibility. The interface is half broken in that > situation anyway and if you're leaking filesystem visibility into a > supposedly isolated container, relaxed resource limits aren't biggest of > your problems. > > While the proposed change isn't necessarily a bad idea, it's a behavior > change and I don't either modifying existing behavior or introducing a new > mount flag is justified here. Maybe just update the documentation indicating > that the ancestral cgroups shouldn't be visible in a delegated ns? > > Thanks. > Thank you, TJ, I will send a patch to update comment and the documentation. Thanks, Ridong