ALSA: usb-audio: Fix unintentional sign extension issue

The shifting of the u8 integer device by 24 bits to the left will
be promoted to a 32 bit signed int and then sign-extended to a
64 bit unsigned long. In the event that the top bit of device is
set then all then all the upper 32 bits of the unsigned long will
end up as also being set because of the sign-extension. Fix this
by casting device to an unsigned long before the shift.

Addresses-Coverity: ("Unintended sign extension")
Fixes: a07df82c7990 ("ALSA: usb-audio: Add DJM750 to Pioneer mixer quirk")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210318132008.15266-1-colin.king@canonical.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index 08873d2..ffd9223 100644 (file)
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -2883,7 +2883,7 @@ static int snd_djm_controls_put(struct snd_kcontrol *kctl, struct snd_ctl_elem_v
        u8 group = (private_value & SND_DJM_GROUP_MASK) >> SND_DJM_GROUP_SHIFT;
        u16 value = elem->value.enumerated.item[0];
 
-       kctl->private_value = ((device << SND_DJM_DEVICE_SHIFT) |
+       kctl->private_value = (((unsigned long)device << SND_DJM_DEVICE_SHIFT) |
                              (group << SND_DJM_GROUP_SHIFT) |
                              value);
 
@@ -2921,7 +2921,7 @@ static int snd_djm_controls_create(struct usb_mixer_interface *mixer,
                value = device->controls[i].default_value;
                knew.name = device->controls[i].name;
                knew.private_value = (
-                       (device_idx << SND_DJM_DEVICE_SHIFT) |
+                       ((unsigned long)device_idx << SND_DJM_DEVICE_SHIFT) |
                        (i << SND_DJM_GROUP_SHIFT) |
                        value);
                err = snd_djm_controls_update(mixer, device_idx, i, value);