[PATCH 5.4.y] comedi: pcl812: Fix bit shift out of bounds

[PATCH 5.4.y] comedi: pcl812: Fix bit shift out of bounds

[Ian Abbott]

[ Upstream commit b14b076ce593f72585412fc7fd3747e03a5e3632 ]

When checking for a supported IRQ number, the following test is used:

	if ((1 << it->options[1]) & board->irq_bits) {

However, `it->options[i]` is an unchecked `int` value from userspace, so
the shift amount could be negative or out of bounds.  Fix the test by
requiring `it->options[1]` to be within bounds before proceeding with
the original test.  Valid `it->options[1]` values that select the IRQ
will be in the range [1,15]. The value 0 explicitly disables the use of
interrupts.

Reported-by: syzbot+32de323b0addb9e114ff@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=32de323b0addb9e114ff
Fixes: fcdb427bc7cf ("Staging: comedi: add pcl821 driver")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250707133429.73202-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/comedi/drivers/pcl812.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/pcl812.c b/drivers/staging/comedi/drivers/pcl812.c
index aefc1b849cf7..98112c79e2d7 100644
--- a/drivers/staging/comedi/drivers/pcl812.c
+++ b/drivers/staging/comedi/drivers/pcl812.c
@@ -1151,7 +1151,8 @@ static int pcl812_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		if (!dev->pacer)
 			return -ENOMEM;
 
-		if ((1 << it->options[1]) & board->irq_bits) {
+		if (it->options[1] > 0 && it->options[1] < 16 &&
+		    (1 << it->options[1]) & board->irq_bits) {
 			ret = request_irq(it->options[1], pcl812_interrupt, 0,
 					  dev->board_name, dev);
 			if (ret == 0)
-- 
2.47.2

Re: [PATCH 5.4.y] comedi: pcl812: Fix bit shift out of bounds

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: b14b076ce593f72585412fc7fd3747e03a5e3632

Status in newer kernel trees:
6.15.y | Not found
6.12.y | Not found
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found
5.10.y | Not found

Note: The patch differs from the upstream commit:
---
1:  b14b076ce593 ! 1:  952eb52a154f comedi: pcl812: Fix bit shift out of bounds
    @@ Metadata
      ## Commit message ##
         comedi: pcl812: Fix bit shift out of bounds
     
    +    [ Upstream commit b14b076ce593f72585412fc7fd3747e03a5e3632 ]
    +
         When checking for a supported IRQ number, the following test is used:
     
                 if ((1 << it->options[1]) & board->irq_bits) {
    @@ Commit message
         Link: https://lore.kernel.org/r/20250707133429.73202-1-abbotti@mev.co.uk
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     
    - ## drivers/comedi/drivers/pcl812.c ##
    -@@ drivers/comedi/drivers/pcl812.c: static int pcl812_attach(struct comedi_device *dev, struct comedi_devconfig *it)
    - 		if (IS_ERR(dev->pacer))
    - 			return PTR_ERR(dev->pacer);
    + ## drivers/staging/comedi/drivers/pcl812.c ##
    +@@ drivers/staging/comedi/drivers/pcl812.c: static int pcl812_attach(struct comedi_device *dev, struct comedi_devconfig *it)
    + 		if (!dev->pacer)
    + 			return -ENOMEM;
      
     -		if ((1 << it->options[1]) & board->irq_bits) {
     +		if (it->options[1] > 0 && it->options[1] < 16 &&

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| origin/linux-5.4.y        | Success     | Success    |