V4L/DVB: cx88-alsa: prevent out-of-range volume setting

Ensure that volume values are always in the allowed range.  Otherwise,
it would be possible to set other bits in the AUD_VOL_CTL register or to
get a wrong sign in the AUD_BAL_CTL register.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/media/video/cx88/cx88-alsa.c b/drivers/media/video/cx88/cx88-alsa.c
index 5a67445dd6ed..64b350df78e3 100644
--- a/drivers/media/video/cx88/cx88-alsa.c
+++ b/drivers/media/video/cx88/cx88-alsa.c
@@ -583,16 +583,18 @@ static int snd_cx88_volume_put(struct snd_kcontrol *kcontrol,
 {
         snd_cx88_card_t *chip = snd_kcontrol_chip(kcontrol);
         struct cx88_core *core=chip->core;
-        int v, b;
+        int left, right, v, b;
         int changed = 0;
         u32 old;
 
-        b = value->value.integer.value[1] - value->value.integer.value[0];
+        left = value->value.integer.value[0] & 0x3f;
+        right = value->value.integer.value[1] & 0x3f;
+        b = right - left;
         if (b < 0) {
-            v = 0x3f - value->value.integer.value[0];
+            v = 0x3f - left;
             b = (-b) | 0x40;
         } else {
-            v = 0x3f - value->value.integer.value[1];
+            v = 0x3f - right;
         }
         /* Do we really know this will always be called with IRQs on? */
         spin_lock_irq(&chip->reg_lock);