linux-kernel - Re: [RFC] Restrict the untrusted devices, to bind to only a set of "whitelisted" drivers

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Message-ID: <20200610230119.GA1528268@bjorn-Precision-5520>
Date:   Wed, 10 Jun 2020 18:01:19 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rajat Jain <rajatxjain@...il.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Krishnakumar, Lalithambika" <lalithambika.krishnakumar@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Prashant Malani <pmalani@...gle.com>,
        Benson Leung <bleung@...gle.com>,
        Todd Broch <tbroch@...gle.com>,
        Alex Levin <levinale@...gle.com>,
        Mattias Nissler <mnissler@...gle.com>,
        Zubin Mithra <zsm@...gle.com>,
        Bernie Keany <bernie.keany@...el.com>,
        Aaron Durbin <adurbin@...gle.com>,
        Diego Rivas <diegorivas@...gle.com>,
        Duncan Laurie <dlaurie@...gle.com>,
        Furquan Shaikh <furquan@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Christian Kellner <christian@...lner.me>,
        Alex Williamson <alex.williamson@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Restrict the untrusted devices, to bind to only a set of
 "whitelisted" drivers

On Tue, Jun 09, 2020 at 05:30:13PM -0700, Rajat Jain wrote:
> On Tue, Jun 9, 2020 at 5:04 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Tue, Jun 09, 2020 at 04:23:54PM -0700, Rajat Jain wrote:
> > > Thanks for sending out the summary, I was about to send it out but got lazy.
> > > ...

> > > The one thing that still needs more thought is how about the
> > > "pcieport" driver that enumerates the PCI bridges. I'm unsure if it
> > > needs to be whitelisted for further enumeration downstream. What do
> > > you think?
> >
> > The pcieport driver is required for AER, PCIe native hotplug, PME,
> > etc., and it cannot be a module, so the whitelist wouldn't apply to
> > it.
> 
> Not that I see the need, but slight clarification needed just to make
> sure I understand it clearly:
> 
> Since pcieport driver is statically compiled in, AER, pciehp, PME, DPC
> etc will always be enabled for devices plugged in during boot. But I
> can still choose to choose to allow or deny for devices added *after
> boot* using the whitelist, right?

Yes, I think so.  However, if pcieport doesn't claim hot-added devices
like a dock, I don't think hotplug of PCI things downstream from the
dock will work, e.g., if there are Thunderbolt switches in a monitor
or something.

> Also, denying pcieport driver for hot-added PCIe bridges only disables
> these pcieport services on those bridges, but device enumeration
> further downstream those bridges is not an issue?

Right.  Devices without pcieport would not be able to report hotplug
events, so we wouldn't notice hot-adds or -removes involving those
devices.