[bug report] ALSA: usb-audio: More validations of descriptor units

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Takashi Iwai,

This is a semi-automatic email about new static checker warnings.

The patch 57f8770620e9: "ALSA: usb-audio: More validations of
descriptor units" from Aug 20, 2019, leads to the following Smatch
complaint:

    sound/usb/quirks.c:254 create_yamaha_midi_quirk()
    warn: variable dereferenced before check 'injd' (see line 251)

sound/usb/quirks.c
   244          /* must have some valid jack descriptors */
   245          injd = snd_usb_find_csint_desc(alts->extra, alts->extralen,
   246                                         NULL, USB_MS_MIDI_IN_JACK);
   247          outjd = snd_usb_find_csint_desc(alts->extra, alts->extralen,
   248                                          NULL, USB_MS_MIDI_OUT_JACK);
   249          if (!injd && !outjd)
                     ^^^^^^^^^^^^^
At least one must be valid.

   250                  return -ENODEV;
   250			return -ENODEV;
   251		if (!snd_usb_validate_midi_desc(injd) ||
   252		    !snd_usb_validate_midi_desc(outjd))

So this should return true/valid if the pointer is NULL?

   253			return -ENODEV;
   254		if (injd && (injd->bLength < 5 ||
   255			     (injd->bJackType != USB_MS_EMBEDDED &&
   256			      injd->bJackType != USB_MS_EXTERNAL)))

regards,
dan carpenter