patch "staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift" added to staging-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From 0bd0db42a030b75c20028c7ba6e327b9cb554116 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 17 Jul 2020 15:52:55 +0100
Subject: staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

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: 33cdce6293dcc ("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>
---
 .../staging/comedi/drivers/addi_apci_1032.c   | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/comedi/drivers/addi_apci_1032.c b/drivers/staging/comedi/drivers/addi_apci_1032.c
index 560649be9d13..e035c9f757a1 100644
--- 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;
-- 
2.27.0