[PATCH 0/4] staging: comedi: INSN_CONFIG_DIGITAL_TRIG fixes

[PATCH 0/4] staging: comedi: INSN_CONFIG_DIGITAL_TRIG fixes

[Ian Abbott]

These patches correct problems with INSN_CONFIG_DIGITAL_TRIG comedi
configuration instructions in various comedi drivers, in particular the
use of unconstrained bit shift amounts from userspace leading to
undefined behaviour (although hopefully not the kernel crashy sort).

The patches have been marked for inclusion in the stable tree.  Note
that patch 4 changes a similar area of code to Dan Carpenter's commit
ef75e14a6c93 ("staging: comedi: verify array index is correct before
using it"), so I have indicated it as a prerequisite.

*Note to Greg KH*: I have based these patches on your "staging-linus"
branch due to the prerequisite ef75e14a6c93 mentioned above being
present in neither "staging-next" nor "staging-testing" at the time of
posting.

1) staging: comedi: ni_6527: fix INSN_CONFIG_DIGITAL_TRIG support
2) staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift
3) staging: comedi: addi_apci_1564: check INSN_CONFIG_DIGITAL_TRIG shift
4) staging: comedi: addi_apci_1500: check INSN_CONFIG_DIGITAL_TRIG shift

 drivers/staging/comedi/drivers/addi_apci_1032.c | 20 ++++++++++++++------
 drivers/staging/comedi/drivers/addi_apci_1500.c | 24 +++++++++++++++++++-----
 drivers/staging/comedi/drivers/addi_apci_1564.c | 20 ++++++++++++++------
 drivers/staging/comedi/drivers/ni_6527.c        |  2 +-
 4 files changed, 48 insertions(+), 18 deletions(-)

[PATCH 1/4] staging: comedi: ni_6527: fix INSN_CONFIG_DIGITAL_TRIG support

[Ian Abbott]

`ni6527_intr_insn_config()` processes `INSN_CONFIG` comedi instructions
for the "interrupt" subdevice.  When `data[0]` is
`INSN_CONFIG_DIGITAL_TRIG` it is configuring the digital trigger.  When
`data[2]` is `COMEDI_DIGITAL_TRIG_ENABLE_EDGES` it is configuring rising
and falling edge detection for the digital trigger, using a base channel
number (or shift amount) in `data[3]`, a rising edge bitmask in
`data[4]` and falling edge bitmask in `data[5]`.

If the base channel number (shift amount) is greater than or equal to
the number of channels (24) of the digital input subdevice, there are no
changes to the rising and falling edges, so the mask of channels to be
changed can be set to 0, otherwise the mask of channels to be changed,
and the rising and falling edge bitmasks are shifted by the base channel
number before calling `ni6527_set_edge_detection()` to change the
appropriate registers.  Unfortunately, the code is comparing the base
channel (shift amount) to the interrupt subdevice's number of channels
(1) instead of the digital input subdevice's number of channels (24).
Fix it by comparing to 32 because all shift amounts for an `unsigned
int` must be less than that and everything from bit 24 upwards is
ignored by `ni6527_set_edge_detection()` anyway.

Fixes: 110f9e687c1a8 ("staging: comedi: ni_6527: support INSN_CONFIG_DIGITAL_TRIG")
Cc: <stable@vger.kernel.org> # 3.17+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
 drivers/staging/comedi/drivers/ni_6527.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/ni_6527.c b/drivers/staging/comedi/drivers/ni_6527.c
index 4d1eccb5041d..4518c2680b7c 100644
--- a/drivers/staging/comedi/drivers/ni_6527.c
+++ b/drivers/staging/comedi/drivers/ni_6527.c
@@ -332,7 +332,7 @@ static int ni6527_intr_insn_config(struct comedi_device *dev,
 		case COMEDI_DIGITAL_TRIG_ENABLE_EDGES:
 			/* check shift amount */
 			shift = data[3];
-			if (shift >= s->n_chan) {
+			if (shift >= 32) {
 				mask = 0;
 				rising = 0;
 				falling = 0;
-- 
2.27.0

[PATCH 2/4] staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

[Ian Abbott]

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>
---
 .../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

[PATCH 3/4] staging: comedi: addi_apci_1564: check INSN_CONFIG_DIGITAL_TRIG shift

[Ian Abbott]

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

diff --git a/drivers/staging/comedi/drivers/addi_apci_1564.c b/drivers/staging/comedi/drivers/addi_apci_1564.c
index 10501fe6bb25..1268ba34be5f 100644
--- a/drivers/staging/comedi/drivers/addi_apci_1564.c
+++ b/drivers/staging/comedi/drivers/addi_apci_1564.c
@@ -331,14 +331,22 @@ static int apci1564_cos_insn_config(struct comedi_device *dev,
 				    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;
@@ -362,8 +370,8 @@ static int apci1564_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 != (APCI1564_DI_IRQ_ENA |
@@ -380,8 +388,8 @@ static int apci1564_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

[PATCH 4/4] staging: comedi: addi_apci_1500: check INSN_CONFIG_DIGITAL_TRIG shift

[Ian Abbott]

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, adjusting the checks
for invalid channels so that enabled channel bits that would have been
lost by shifting are also checked for validity.  Only channels 0 to 15
are valid.

Fixes: a8c66b684efaf ("staging: comedi: addi_apci_1500: rewrite the subdevice support functions")
Cc: <stable@vger.kernel.org> #4.0+: ef75e14a6c93: staging: comedi: verify array index is correct before using it
Cc: <stable@vger.kernel.org> #4.0+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
 .../staging/comedi/drivers/addi_apci_1500.c   | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/comedi/drivers/addi_apci_1500.c b/drivers/staging/comedi/drivers/addi_apci_1500.c
index 689acd69a1b9..816dd25b9d0e 100644
--- a/drivers/staging/comedi/drivers/addi_apci_1500.c
+++ b/drivers/staging/comedi/drivers/addi_apci_1500.c
@@ -452,13 +452,14 @@ static int apci1500_di_cfg_trig(struct comedi_device *dev,
 	struct apci1500_private *devpriv = dev->private;
 	unsigned int trig = data[1];
 	unsigned int shift = data[3];
-	unsigned int hi_mask = data[4] << shift;
-	unsigned int lo_mask = data[5] << shift;
-	unsigned int chan_mask = hi_mask | lo_mask;
-	unsigned int old_mask = (1 << shift) - 1;
+	unsigned int hi_mask;
+	unsigned int lo_mask;
+	unsigned int chan_mask;
+	unsigned int old_mask;
 	unsigned int pm;
 	unsigned int pt;
 	unsigned int pp;
+	unsigned int invalid_chan;
 
 	if (trig > 1) {
 		dev_dbg(dev->class_dev,
@@ -466,7 +467,20 @@ static int apci1500_di_cfg_trig(struct comedi_device *dev,
 		return -EINVAL;
 	}
 
-	if (chan_mask > 0xffff) {
+	if (shift <= 16) {
+		hi_mask = data[4] << shift;
+		lo_mask = data[5] << shift;
+		old_mask = (1U << shift) - 1;
+		invalid_chan = (data[4] | data[5]) >> (16 - shift);
+	} else {
+		hi_mask = 0;
+		lo_mask = 0;
+		old_mask = 0xffff;
+		invalid_chan = data[4] | data[5];
+	}
+	chan_mask = hi_mask | lo_mask;
+
+	if (invalid_chan) {
 		dev_dbg(dev->class_dev, "invalid digital trigger channel\n");
 		return -EINVAL;
 	}
-- 
2.27.0

Re: [PATCH 0/4] staging: comedi: INSN_CONFIG_DIGITAL_TRIG fixes

[Greg Kroah-Hartman]

On Fri, Jul 17, 2020 at 03:52:53PM +0100, Ian Abbott wrote:
> These patches correct problems with INSN_CONFIG_DIGITAL_TRIG comedi
> configuration instructions in various comedi drivers, in particular the
> use of unconstrained bit shift amounts from userspace leading to
> undefined behaviour (although hopefully not the kernel crashy sort).
> 
> The patches have been marked for inclusion in the stable tree.  Note
> that patch 4 changes a similar area of code to Dan Carpenter's commit
> ef75e14a6c93 ("staging: comedi: verify array index is correct before
> using it"), so I have indicated it as a prerequisite.
> 
> *Note to Greg KH*: I have based these patches on your "staging-linus"
> branch due to the prerequisite ef75e14a6c93 mentioned above being
> present in neither "staging-next" nor "staging-testing" at the time of
> posting.

Thanks for the note, all now queued up to the proper branch.

greg k-h