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Subject[PATCH 4.4 31/54] staging: comedi: addi_apci_1564: check INSN_CONFIG_DIGITAL_TRIG shift
Date
From: Ian Abbott <abbotti@mev.co.uk>

commit 926234f1b8434c4409aa4c53637aa3362ca07cea 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: 1e15687ea472 ("staging: comedi: addi_apci_1564: add Change-of-State interrupt subdevice and required functions")
Cc: <stable@vger.kernel.org> #3.17+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20200717145257.112660-4-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/comedi/drivers/addi_apci_1564.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)

--- a/drivers/staging/comedi/drivers/addi_apci_1564.c
+++ b/drivers/staging/comedi/drivers/addi_apci_1564.c
@@ -288,14 +288,22 @@ static int apci1564_cos_insn_config(stru
unsigned int *data)
{
struct apci1564_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;
@@ -319,8 +327,8 @@ static int apci1564_cos_insn_config(stru
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 != (APCI1564_DI_IRQ_ENA |
@@ -337,8 +345,8 @@ static int apci1564_cos_insn_config(stru
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;

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