staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

ian-abbott · gregkh · commit 97ab1fd6d47f · 2020-07-29T10:16:55.000+02:00
commit 0bd0db4 upstream. The `INSN_CONFIG` comedi instruction with sub-instruction code `INSN_CONFIG_DIGITAL_TRIG` includes a base channel in `data[3]`. This is used as a right shift amount for other bitmask values without being checked. Shift amounts greater than or equal to 32 will result in undefined behavior. Add code to deal with this. Fixes: 33cdce6 ("staging: comedi: addi_apci_1032: conform to new INSN_CONFIG_DIGITAL_TRIG") Cc: <stable@vger.kernel.org> #3.8+ Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Link: https://lore.kernel.org/r/20200717145257.112660-3-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/comedi/drivers/addi_apci_1032.c b/drivers/staging/comedi/drivers/addi_apci_1032.c
@@ -106,14 +106,22 @@ static int apci1032_cos_insn_config(struct comedi_device *dev,
 				    unsigned int *data)
 {
 	struct apci1032_private *devpriv = dev->private;
-	unsigned int shift, oldmask;
+	unsigned int shift, oldmask, himask, lomask;
 
 	switch (data[0]) {
 	case INSN_CONFIG_DIGITAL_TRIG:
 		if (data[1] != 0)
 			return -EINVAL;
 		shift = data[3];
-		oldmask = (1U << shift) - 1;
+		if (shift < 32) {
+			oldmask = (1U << shift) - 1;
+			himask = data[4] << shift;
+			lomask = data[5] << shift;
+		} else {
+			oldmask = 0xffffffffu;
+			himask = 0;
+			lomask = 0;
+		}
 		switch (data[2]) {
 		case COMEDI_DIGITAL_TRIG_DISABLE:
 			devpriv->ctrl = 0;
@@ -136,8 +144,8 @@ static int apci1032_cos_insn_config(struct comedi_device *dev,
 				devpriv->mode2 &= oldmask;
 			}
 			/* configure specified channels */
-			devpriv->mode1 |= data[4] << shift;
-			devpriv->mode2 |= data[5] << shift;
+			devpriv->mode1 |= himask;
+			devpriv->mode2 |= lomask;
 			break;
 		case COMEDI_DIGITAL_TRIG_ENABLE_LEVELS:
 			if (devpriv->ctrl != (APCI1032_CTRL_INT_ENA |
@@ -154,8 +162,8 @@ static int apci1032_cos_insn_config(struct comedi_device *dev,
 				devpriv->mode2 &= oldmask;
 			}
 			/* configure specified channels */
-			devpriv->mode1 |= data[4] << shift;
-			devpriv->mode2 |= data[5] << shift;
+			devpriv->mode1 |= himask;
+			devpriv->mode2 |= lomask;
 			break;
 		default:
 			return -EINVAL;
