Re: [PATCH 4.19 062/125] ALSA: usb-audio: Fix possible NULL dereference at create_yamaha_midi_quirk()

Hi!

From: Takashi Iwai tiwai@suse.de

commit 60849562a5db4a1eee2160167e4dce4590d3eafe upstream.

The previous addition of descriptor validation may lead to a NULL dereference at create_yamaha_midi_quirk() when either injd or outjd is NULL. Add proper non-NULL checks.

This is wrong.

@@ -259,8 +259,8 @@ static int create_yamaha_midi_quirk(stru NULL, USB_MS_MIDI_OUT_JACK); if (!injd && !outjd) return -ENODEV;

Clearly code wants to allow at most one of them to be NULL.

• if (!snd_usb_validate_midi_desc(injd) ||

•    !snd_usb_validate_midi_desc(outjd))
  

• if (!(injd && snd_usb_validate_midi_desc(injd)) ||

•    !(outjd && snd_usb_validate_midi_desc(outjd)))
  

  return -ENODEV;

Yet it will return here if it is. Correct check would be

+ if (!(!injd || snd_usb_validate_midi_desc(injd)) || + !(!outjd || snd_usb_validate_midi_desc(outjd)))

AFAICT.

Best regards, Pavel