Re: [PATCH 1/2] HID: logitech-hidpp: do not return the name length

Peter Wu
2014-12-10T22:53:48Z

On Wednesday 10 December 2014 17:21:09 Benjamin Tissoires wrote:
> We do not make any use of the actual name length get through
> hidpp_get_device_name().
>
> We can drop the extra code and simplify the API a bit.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
>
> ---
> drivers/hid/hid-logitech-hidpp.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 1a6395d..3846305 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -461,7 +461,7 @@ static int hidpp_devicenametype_get_device_name(struct hidpp_device *hidpp,
> return count;
> }
>
> -static char *hidpp_get_device_name(struct hidpp_device *hidpp, u8 *name_length)
> +static char *hidpp_get_device_name(struct hidpp_device *hidpp)
> {
> u8 feature_type;
> u8 feature_index;
> @@ -484,7 +484,6 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp, u8 *name_length)
> if (!name)
> goto out_err;
>
> - *name_length = __name_length + 1;
> while (index < __name_length)
> index += hidpp_devicenametype_get_device_name(hidpp,
> feature_index, index, name + index,

hidpp_devicenametype_get_device_name can return a non-positive value if
the USB device is unplugged at the wrong time, or if a malicious device
is attached (and 0 is returned). An infinite loop is the result.

Can you apply this change in the patch or should I send you a separate
one?

while (index < __name_length) {
ret = hidpp_devicenametype_get_device_name(hidpp,
feature_index, index, name + index,
__name_length - index);
if (ret <= 0) {
kfree(name);
return NULL;
}
index += ret;
}

> @@ -493,7 +492,6 @@ static char *hidpp_get_device_name(struct hidpp_device *hidpp, u8 *name_length)
> return name;
>
> out_err:
> - *name_length = 0;
> return NULL;

What about dropping the label out_err here and returning NULL in the
previous places?

> }
>
> @@ -989,7 +987,6 @@ static void hidpp_overwrite_name(struct hid_device *hdev, bool use_unifying)
> {
> struct hidpp_device *hidpp = hid_get_drvdata(hdev);
> char *name;
> - u8 name_length;
>
> if (use_unifying)
> /*
> @@ -999,7 +996,7 @@ static void hidpp_overwrite_name(struct hid_device *hdev, bool use_unifying)
> */
> name = hidpp_get_unifying_name(hidpp);
> else
> - name = hidpp_get_device_name(hidpp, &name_length);
> + name = hidpp_get_device_name(hidpp);
>
> if (!name)
> hid_err(hdev, "unable to retrieve the name of the device");
> @@ -1053,7 +1050,6 @@ static void hidpp_connect_event(struct hidpp_device *hidpp)
> bool connected = atomic_read(&hidpp->connected);
> struct input_dev *input;
> char *name, *devm_name;
> - u8 name_length;
>
> if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)
> wtp_connect(hdev, connected);
> @@ -1080,7 +1076,7 @@ static void hidpp_connect_event(struct hidpp_device *hidpp)
> return;
> }
>
> - name = hidpp_get_device_name(hidpp, &name_length);
> + name = hidpp_get_device_name(hidpp);
> if (!name) {
> hid_err(hdev, "unable to retrieve the name of the device");
> } else {
>