[PATCH 5.10 035/157] ALSA: usb-audio: Fix unintentional sign extension issue

Greg Kroah-Hartman
2021-03-22T12:46:42Z

From: Colin Ian King <colin.king@canonical.com>

commit 50b1affc891cbc103a2334ce909a026e25f4c84d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/usb/mixer_quirks.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -2883,7 +2883,7 @@ static int snd_djm_controls_put(struct s
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(struc
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);