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

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Date:   Wed, 10 Jun 2020 16:46:37 -0700
From:   Rajat Jain <rajatja@...gle.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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 Wed, Jun 10, 2020 at 4:01 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> 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.

Yes, understood, thanks.

>
> > 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.

Understood.

Thanks,

Rajat