Re: [PATCH RFT] ieee802154: atusb: move to new USB API

[Alexander Aring <alex.aring@gmail.com>]

Hi,

On Mon, 3 Jan 2022 at 08:03, Greg KH <greg@kroah.com> wrote:
>
> On Sun, Jan 02, 2022 at 08:19:43PM +0300, Pavel Skripkin wrote:
> > Alexander reported a use of uninitialized value in
> > atusb_set_extended_addr(), that is caused by reading 0 bytes via
> > usb_control_msg().
> >
> > Since there is an API, that cannot read less bytes, than was requested,
> > let's move atusb driver to use it. It will fix all potintial bugs with
> > uninit values and make code more modern
> >
> > Fail log:
> >
> > BUG: KASAN: uninit-cmp in ieee802154_is_valid_extended_unicast_addr include/linux/ieee802154.h:310 [inline]
> > BUG: KASAN: uninit-cmp in atusb_set_extended_addr drivers/net/ieee802154/atusb.c:1000 [inline]
> > BUG: KASAN: uninit-cmp in atusb_probe.cold+0x29f/0x14db drivers/net/ieee802154/atusb.c:1056
> > Uninit value used in comparison: 311daa649a2003bd stack handle: 000000009a2003bd
> >  ieee802154_is_valid_extended_unicast_addr include/linux/ieee802154.h:310 [inline]
> >  atusb_set_extended_addr drivers/net/ieee802154/atusb.c:1000 [inline]
> >  atusb_probe.cold+0x29f/0x14db drivers/net/ieee802154/atusb.c:1056
> >  usb_probe_interface+0x314/0x7f0 drivers/usb/core/driver.c:396
> >
> > Fixes: 7490b008d123 ("ieee802154: add support for atusb transceiver")
> > Cc: stable@vger.kernel.org # 5.9
> > Reported-by: Alexander Potapenko <glider@google.com>
> > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> > ---
> >  drivers/net/ieee802154/atusb.c | 61 +++++++++++++++++++++-------------
> >  1 file changed, 38 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/net/ieee802154/atusb.c b/drivers/net/ieee802154/atusb.c
> > index 23ee0b14cbfa..43befea0110f 100644
> > --- a/drivers/net/ieee802154/atusb.c
> > +++ b/drivers/net/ieee802154/atusb.c
> > @@ -80,10 +80,9 @@ struct atusb_chip_data {
> >   * in atusb->err and reject all subsequent requests until the error is cleared.
> >   */
> >
> > -static int atusb_control_msg(struct atusb *atusb, unsigned int pipe,
> > -                          __u8 request, __u8 requesttype,
> > -                          __u16 value, __u16 index,
> > -                          void *data, __u16 size, int timeout)
> > +static int atusb_control_msg_recv(struct atusb *atusb, __u8 request, __u8 requesttype,
> > +                               __u16 value, __u16 index,
> > +                               void *data, __u16 size, int timeout)
>
> Why do you need a wrapper function at all?  Why not just call the real
> usb functions instead?
>

This driver has a lot of history, there is a comment which states:

"To reduce the number of error checks in the code, we record the first
error in atusb->err and reject all subsequent requests until the error
is cleared."

I think in the early state of this driver (as it was acting more as an
USB<->SPI bridge) there was a lot of state handling involved. Nowadays
we have a lot of such handling inside the device firmware (which is
btw. open source). This might be not an excuse but an explanation why
it was introduced in such a way.

...
>
> I would recommend just moving to use the real USB functions and no
> wrapper function at all like this, it will make things more obvious and
> easier to understand over time.

okay.

- Alex