comedi: das6402: Fix bit shift out of bounds

commit 70f2b28b5243df557f51c054c20058ae207baaac upstream.

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

	/* IRQs 2,3,5,6,7, 10,11,15 are valid for "enhanced" mode */
	if ((1 << it->options[1]) & 0x8cec) {

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.

Fixes: 79e5e6ad ("staging: comedi: das6402: rewrite broken driver")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250707135737.77448-1-abbotti@mev.co.uk


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>