comedi: pcl812: Fix bit shift out of bounds

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>

diff --git a/drivers/comedi/drivers/pcl812.c b/drivers/comedi/drivers/pcl812.c
index 0df639c6a595e5e36ad2a7c28c90f4cccc6069bb..abca61a72cf7eafcb6b13bd37c84c57b1f2e3bd0 100644 (file)
--- a/drivers/comedi/drivers/pcl812.c
+++ b/drivers/comedi/drivers/pcl812.c
@@ -1149,7 +1149,8 @@ static int pcl812_attach(struct comedi_device *dev, struct comedi_devconfig *it)
                if (IS_ERR(dev->pacer))
                        return PTR_ERR(dev->pacer);
 
-               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)