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

Benjamin Tissoires
2014-12-10T23:19:56Z

On Dec 10 2014 or thereabouts, Peter Wu wrote:
> 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.

Oh, yes, you are definitively right.

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

Feel free to send your patch directly to the list.

>
> 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?

Yep, good idea. You can either send a patch for that if you want to take
credits, or I can send a v2. It's up to you.

Cheers,
Benjamin

>
> > }
> >
> > @@ -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 {
> >
>