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SubjectRe: [PATCH] platform/x86: wmi: fix potential null pointer dereferences
On Tue, Jan 22, 2019 at 10:04 PM Mattias Jacobsson <2pi@mok.nu> wrote:
>
> In the function wmi_dev_match() there are three variables that
> potentially can result in a null pointer dereference. Namely:
> dev/wblock, driver/wmi_driver, and wmi_driver->id_table.
>
> Check for NULL and return that the driver can't handle the device if any
> of these variables would result in a null pointer dereference.
>
> The NULL checks are performed prior to running container_of() for the
> variables dev/wblock and driver/wmi_driver.
>
> Fixes: 844af950da94 ("platform/x86: wmi: Turn WMI into a bus driver")
> Signed-off-by: Mattias Jacobsson <2pi@mok.nu>
> ---
> drivers/platform/x86/wmi.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index bea35be68706..c596479e8b13 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -763,10 +763,18 @@ static void wmi_dev_release(struct device *dev)
>
> static int wmi_dev_match(struct device *dev, struct device_driver *driver)
> {
> - struct wmi_driver *wmi_driver =
> - container_of(driver, struct wmi_driver, driver);

AFAIU this is just a pointer arithmetics, no need to move it.

> - struct wmi_block *wblock = dev_to_wblock(dev);

> - const struct wmi_device_id *id = wmi_driver->id_table;
> + const struct wmi_device_id *id;
> + struct wmi_block *wblock;
> + struct wmi_driver *wmi_driver;
> +

> + if (dev == NULL || driver == NULL)
> + return 0;

On which circumstances this may ever happen?

> + wblock = dev_to_wblock(dev);
> + wmi_driver = container_of(driver, struct wmi_driver, driver);
> +
> + if (wmi_driver->id_table == NULL)
> + return 0;
> + id = wmi_driver->id_table;
>
> while (id->guid_string) {
> uuid_le driver_guid;
> --
> 2.20.1
>


--
With Best Regards,
Andy Shevchenko

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