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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 DC407C433E2 for ; Wed, 10 Jun 2020 07:12:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B81812083B for ; Wed, 10 Jun 2020 07:12:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591773169; bh=pd2SzRJOzTRtTej8TfH3UhWrXB1jr/uVuRtkc+0eAOU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=XiSDmLxicnZjGyXoSpngp+Vro5xRRzwsUEHUSQ7Us6wYQC/j8sDsGGHHnJLv05gsq CZmDUdPBiHrwwjgxNVQCDODtIpThzIsC3C9ofyUd7XkpGDBbX3heBwEwgzTWfOmQRf bTHkjJWunctOgevjhY1c6cfH5EHIoFws2cB63P/8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbgFJHMo (ORCPT ); Wed, 10 Jun 2020 03:12:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:52278 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726276AbgFJHMm (ORCPT ); Wed, 10 Jun 2020 03:12:42 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 32D712081A; Wed, 10 Jun 2020 07:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591773161; bh=pd2SzRJOzTRtTej8TfH3UhWrXB1jr/uVuRtkc+0eAOU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nyf/eaZLnteXhDufaX0guURN6YQMM5b4xLIKTqUyDX+XZpu7kzrS0c7MBd3ngO68k oAxc3ugpBuJAZ/sFm9TRa9PtPBCPFrvl6H/I+GdzF+zL3SDt5XEYjnYTmlTTQESjGM h/C2gY/gyXKnf02ev6qeBwVP9ZMYkbze0nAhUb7U= Date: Wed, 10 Jun 2020 09:12:39 +0200 From: Greg Kroah-Hartman To: Bjorn Helgaas Cc: Rajat Jain , Rajat Jain , "Raj, Ashok" , "Krishnakumar, Lalithambika" , Bjorn Helgaas , linux-pci , Mika Westerberg , Jean-Philippe Brucker , Prashant Malani , Benson Leung , Todd Broch , Alex Levin , Mattias Nissler , Zubin Mithra , Bernie Keany , Aaron Durbin , Diego Rivas , Duncan Laurie , Furquan Shaikh , Jesse Barnes , Christian Kellner , Alex Williamson , Joerg Roedel , Linux Kernel Mailing List Subject: Re: [RFC] Restrict the untrusted devices, to bind to only a set of "whitelisted" drivers Message-ID: <20200610071239.GC1923109@kroah.com> References: <20200607113632.GA49147@kroah.com> <20200609210400.GA1461839@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200609210400.GA1461839@bjorn-Precision-5520> Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Jun 09, 2020 at 04:04:00PM -0500, Bjorn Helgaas wrote: > On Sun, Jun 07, 2020 at 01:36:32PM +0200, Greg Kroah-Hartman wrote: > > > Your "problem" I think can be summed up a bit more concise: > > - you don't trust kernel drivers to be "secure" for untrusted > > devices > > - you only want to bind kernel drivers to "internal" devices > > automatically as you "trust" drivers in that situation. > > - you want to only bind specific kernel drivers that you somehow > > feel are "secure" to untrusted devices "outside" of a system > > when those devices are added to the system. > > > > Is that correct? > > > > If so, fine, you can do that today with the bind/unbind ability of > > drivers, right? After boot with your "trusted" drivers bound to > > "internal" devices, turn off autobind of drivers to devices and then > > manually bind them when you see new devices show up, as those "must" be > > from external devices (see the bind/unbind files that all drivers export > > for how to do this, and old lwn.net articles, this feature has been > > around for a very long time.) > > > > I know for USB you can do this, odds are PCI you can turn off > > autobinding as well, as I think this is a per-bus flag somewhere. If > > that's not exported to userspace, should be trivial to do so, should be > > somewere in the driver model already... > > > > Ah, yes, look at the "drivers_autoprobe" and "drivers_probe" files in > > sysfs for all busses. Do those not work for you? > > > > My other points are the fact that you don't want to put policy in the > > kernel, and I think that you can do everything you want in userspace > > today, except maybe the fact that trying to determine what is "inside" > > and "outside" is not always easy given that most hardware does not > > export this information properly, if at all. Go work with the firmware > > people on that issue please, that would be most helpful for everyone > > involved to get that finally straightened out. > > To sketch this out, my understanding of how this would work is: > > - Expose the PCI pdev->untrusted bit in sysfs. We don't expose this > today, but doing so would be trivial. I think I would prefer a > sysfs name like "external" so it's more descriptive and less of a > judgment. > > This comes from either the DT "external-facing" property or the > ACPI "ExternalFacingPort" property. Good idea, but as people have pointed out, even these don't always work so userspace will need to be able to override that somehow :( > - All devices present at boot are enumerated. Any statically built > drivers will bind to them before any userspace code runs. > > If you want to keep statically built drivers from binding, you'd > need to invent some mechanism so pci_driver_init() could clear > drivers_autoprobe after registering pci_bus_type. > > - Early userspace code prevents modular drivers from automatically > binding to PCI devices: > > echo 0 > /sys/bus/pci/drivers_autoprobe > > This prevents modular drivers from binding to all devices, whether > present at boot or hot-added. > > - Userspace code uses the sysfs "bind" file to control which drivers > are loaded and can bind to each device, e.g., > > echo 0000:02:00.0 > /sys/bus/pci/drivers/nvme/bind Seems good to me, and also matches what the current USB tools do for this type of thing. thanks, greg k-h