Re: [PATCH] HID: intel-ish-hid: Fix kernel panic during warm reset

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

On Sun, 2023-03-26 at 20:23 -0700, Tanu Malhotra wrote:

some minor nits below.

> During warm reset device->fw_client is set to NULL. If a bus driver
> is
> registered after this NULL setting and before new firmware clients
> are
> enumerated by ISHTP, kernel panic will result in the function
> ishtp_cl_bus_match(). This is because of reference to
> device->fw_client->props.protocol_name.
> 
> ISH firmware after getting successfully loaded, sends a warm reset
> notification to remove all clients from the bus and sets
> device->fw_client to NULL. Until kernel v5.15, all enabled ISHTP
> kernel
> module drivers were loaded after any of the first ISHTP device was
> registered, regardless of whether it was a matched or an unmatched
> device. This resulted in all drivers getting registered much before
> the
> warm reset notification from ISH. Starting kernel v5.16, this issue
> got
> exposed after the change was introduced to load only bus drivers for
> the
> respective matching devices.
One paragraph break will be better.

>  In this scenario, cros_ec_ishtp device and
> cros_ec_ishtp driver are registered after the warm reset
> device_fw_client NULL setting. cros_ec_ishtp driver_register()
> triggers
> the callback to ishtp_cl_bus_match() to match driver to the device
> and
> causes kernel panic in guid_equal() when dereferencing fw_client NULL
> pointer to get protocol_name.
> 
> Fixes: f155dfeaa4ee ("platform/x86: isthp_eclite: only load for
> matching devices")
> Fixes: facfe0a4fdce ("platform/chrome: chros_ec_ishtp: only load for
> matching devices")
> Fixes: 0d0cccc0fd83 ("HID: intel-ish-hid: hid-client: only load for
> matching devices")
> Fixes: 44e2a58cb880 ("HID: intel-ish-hid: fw-loader: only load for
> matching devices")
> 
No need of blank line.

> Signed-off-by: Tanu Malhotra <tanu.malhotra@intel.com>
> Tested-by: Shaunak Saha <shaunak.saha@intel.com>
You can also add 
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>


Also add
Cc: <stable@vger.kernel.org> # 5.16+

> ---
When you submit "PATCH v2", Add change log here. (That is below "---").
Something like this:
v2
- Updated commit description
- Added CC to stable

>  drivers/hid/intel-ish-hid/ishtp/bus.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hid/intel-ish-hid/ishtp/bus.c
> b/drivers/hid/intel-ish-hid/ishtp/bus.c
> index 81385ab37fa9..4f540906268f 100644
> --- a/drivers/hid/intel-ish-hid/ishtp/bus.c
> +++ b/drivers/hid/intel-ish-hid/ishtp/bus.c
> @@ -241,8 +241,8 @@ static int ishtp_cl_bus_match(struct device *dev,
> struct device_driver *drv)
>         struct ishtp_cl_device *device = to_ishtp_cl_device(dev);
>         struct ishtp_cl_driver *driver = to_ishtp_cl_driver(drv);
>  
> -       return guid_equal(&driver->id[0].guid,
> -                         &device->fw_client->props.protocol_name);
> +       return(device->fw_client ? guid_equal(&driver->id[0].guid,
> +                                 &device->fw_client-
> >props.protocol_name) : 0);
Align the second line to char "d" after "(".

Thanks,
Srinivas

>  }
>  
>  /**