comedi: pcl812: Fix bit shift out of bounds

commit b14b076ce593f72585412fc7fd3747e03a5e3632 upstream.

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: fcdb427b ("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>