linux-kernel - Re: [PATCH v2 2/6] driver core: Add common support to skip probe for un-authorized devices

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Date:   Thu, 30 Sep 2021 06:59:36 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Jason Wang <jasowang@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-usb@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 2/6] driver core: Add common support to skip probe for
 un-authorized devices

On Wed, Sep 29, 2021 at 06:05:07PM -0700, Kuppuswamy Sathyanarayanan wrote:
> While the common case for device-authorization is to skip probe of
> unauthorized devices, some buses may still want to emit a message on
> probe failure (Thunderbolt), or base probe failures on the
> authorization status of a related device like a parent (USB). So add
> an option (has_probe_authorization) in struct bus_type for the bus
> driver to own probe authorization policy.
> 
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>



So what e.g. the PCI patch
https://lore.kernel.org/all/CACK8Z6E8pjVeC934oFgr=VB3pULx_GyT2NkzAogdRQJ9TKSX9A@mail.gmail.com/
actually proposes is a list of
allowed drivers, not devices. Doing it at the device level
has disadvantages, for example some devices might have a legacy
unsafe driver, or an out of tree driver. It also does not
address drivers that poke at hardware during init.

Accordingly, I think the right thing to do is to skip
driver init for disallowed drivers, not skip probe
for specific devices.


> ---
>  drivers/base/dd.c            | 5 +++++
>  drivers/thunderbolt/domain.c | 1 +
>  drivers/usb/core/driver.c    | 1 +
>  include/linux/device/bus.h   | 4 ++++
>  4 files changed, 11 insertions(+)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 68ea1f949daa..0cd03ac7d3b1 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -544,6 +544,11 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>  			   !drv->suppress_bind_attrs;
>  	int ret;
>  
> +	if (!dev->authorized && !dev->bus->has_probe_authorization) {
> +		dev_dbg(dev, "Device is not authorized\n");
> +		return -ENODEV;
> +	}
> +
>  	if (defer_all_probes) {
>  		/*
>  		 * Value of defer_all_probes can be set only by
> diff --git a/drivers/thunderbolt/domain.c b/drivers/thunderbolt/domain.c
> index 3e39686eff14..6de8a366b796 100644
> --- a/drivers/thunderbolt/domain.c
> +++ b/drivers/thunderbolt/domain.c
> @@ -321,6 +321,7 @@ struct bus_type tb_bus_type = {
>  	.probe = tb_service_probe,
>  	.remove = tb_service_remove,
>  	.shutdown = tb_service_shutdown,
> +	.has_probe_authorization = true,
>  };
>  
>  static void tb_domain_release(struct device *dev)
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index fb476665f52d..f57b5a7a90ca 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -2028,4 +2028,5 @@ struct bus_type usb_bus_type = {
>  	.match =	usb_device_match,
>  	.uevent =	usb_uevent,
>  	.need_parent_lock =	true,
> +	.has_probe_authorization = true,
>  };
> diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
> index 062777a45a74..571a2f6e7c1d 100644
> --- a/include/linux/device/bus.h
> +++ b/include/linux/device/bus.h
> @@ -69,6 +69,9 @@ struct fwnode_handle;
>   * @lock_key:	Lock class key for use by the lock validator
>   * @need_parent_lock:	When probing or removing a device on this bus, the
>   *			device core should lock the device's parent.
> + * @has_probe_authorization: Set true to indicate to the driver-core to skip
> + *			     the authorization checks and let bus drivers
> + *			     handle it locally.
>   *
>   * A bus is a channel between the processor and one or more devices. For the
>   * purposes of the device model, all devices are connected via a bus, even if
> @@ -112,6 +115,7 @@ struct bus_type {
>  	struct lock_class_key lock_key;
>  
>  	bool need_parent_lock;
> +	bool has_probe_authorization;
>  };
>  
>  extern int __must_check bus_register(struct bus_type *bus);
> -- 
> 2.25.1