Re: [PATCH 06/12] platform/wmi: use generic driver_override infrastructure

[Armin Wolf <W_Armin@xxxxxx>]

Am 24.03.26 um 01:59 schrieb Danilo Krummrich:

> When a driver is probed through __driver_attach(), the bus' match()
> callback is called without the device lock held, thus accessing the
> driver_override field without a lock, which can cause a UAF.
>
> Fix this by using the driver-core driver_override infrastructure taking
> care of proper locking internally.
>
> Note that calling match() from __driver_attach() without the device lock
> held is intentional. [1]
Reviewed-by: Armin Wolf <W_Armin@xxxxxx>

> Link: 
> https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@xxxxxxxxxx/ [1]
> Reported-by: Gui-Dong Han <hanguidong02@xxxxxxxxx>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
> Fixes: 12046f8c77e0 ("platform/x86: wmi: Add driver_override support")
> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
> ---
>   drivers/platform/wmi/core.c | 36 +++++-------------------------------
>   include/linux/wmi.h         |  4 ----
>   2 files changed, 5 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/platform/wmi/core.c b/drivers/platform/wmi/core.c
> index b8e6b9a421c6..750e3619724e 100644
> --- a/drivers/platform/wmi/core.c
> +++ b/drivers/platform/wmi/core.c
> @@ -842,39 +842,11 @@ static ssize_t expensive_show(struct device *dev,
>   }
>   static DEVICE_ATTR_RO(expensive);
>   
> -static ssize_t driver_override_show(struct device *dev, struct device_attribute *attr,
> -                                   char *buf)
> -{
> -       struct wmi_device *wdev = to_wmi_device(dev);
> -       ssize_t ret;
> -
> -       device_lock(dev);
> -       ret = sysfs_emit(buf, "%s\n", wdev->driver_override);
> -       device_unlock(dev);
> -
> -       return ret;
> -}
> -
> -static ssize_t driver_override_store(struct device *dev, struct 
> device_attribute *attr,
> -                                    const char *buf, size_t count)
> -{
> -       struct wmi_device *wdev = to_wmi_device(dev);
> -       int ret;
> -
> -       ret = driver_set_override(dev, &wdev->driver_override, buf, count);
> -       if (ret < 0)
> -               return ret;
> -
> -       return count;
> -}
> -static DEVICE_ATTR_RW(driver_override);
> -
>   static struct attribute *wmi_attrs[] = {
>         &dev_attr_modalias.attr,
>         &dev_attr_guid.attr,
>         &dev_attr_instance_count.attr,
>         &dev_attr_expensive.attr,
> -       &dev_attr_driver_override.attr,
>         NULL
>   };
>   ATTRIBUTE_GROUPS(wmi);
> @@ -943,7 +915,6 @@ static void wmi_dev_release(struct device *dev)
>   {
>         struct wmi_block *wblock = dev_to_wblock(dev);
>   
> -	kfree(wblock->dev.driver_override);
>         kfree(wblock);
>   }
>   
> @@ -952,10 +923,12 @@ static int wmi_dev_match(struct device *dev, const struct device_driver *driver)
>         const struct wmi_driver *wmi_driver = to_wmi_driver(driver);
>         struct wmi_block *wblock = dev_to_wblock(dev);
>         const struct wmi_device_id *id = wmi_driver->id_table;
> +       int ret;
>   
>   	/* When driver_override is set, only bind to the matching driver */
> -       if (wblock->dev.driver_override)
> -               return !strcmp(wblock->dev.driver_override, driver->name);
> +       ret = device_match_driver_override(dev, driver);
> +       if (ret >= 0)
> +               return ret;
>   
>   	if (id == NULL)
>                 return 0;
> @@ -1076,6 +1049,7 @@ static struct class wmi_bus_class = {
>   static const struct bus_type wmi_bus_type = {
>         .name = "wmi",
>         .dev_groups = wmi_groups,
> +       .driver_override = true,
>         .match = wmi_dev_match,
>         .uevent = wmi_dev_uevent,
>         .probe = wmi_dev_probe,
> diff --git a/include/linux/wmi.h b/include/linux/wmi.h
> index 75cb0c7cfe57..14fb644e1701 100644
> --- a/include/linux/wmi.h
> +++ b/include/linux/wmi.h
> @@ -18,16 +18,12 @@
>    * struct wmi_device - WMI device structure
>    * @dev: Device associated with this WMI device
>    * @setable: True for devices implementing the Set Control Method
> - * @driver_override: Driver name to force a match; do not set directly,
> - *                  because core frees it; use driver_set_override() to
> - *                  set or clear it.
>    *
>    * This represents WMI devices discovered by the WMI driver core.
>    */
>   struct wmi_device {
>         struct device dev;
>         bool setable;
> -       const char *driver_override;
>   };
>   
>   /**