comedi: das6402: Fix bit shift out of bounds

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: 79e5e6addbb1 ("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>

diff --git a/drivers/comedi/drivers/das6402.c b/drivers/comedi/drivers/das6402.c
index 68f95330de45fd4dd7c753c2bb74ffd595686bbe..7660487e563c562005ed847775d56eac5a7ed905 100644 (file)
--- a/drivers/comedi/drivers/das6402.c
+++ b/drivers/comedi/drivers/das6402.c
@@ -567,7 +567,8 @@ static int das6402_attach(struct comedi_device *dev,
        das6402_reset(dev);
 
        /* IRQs 2,3,5,6,7, 10,11,15 are valid for "enhanced" mode */
-       if ((1 << it->options[1]) & 0x8cec) {
+       if (it->options[1] > 0 && it->options[1] < 16 &&
+           (1 << it->options[1]) & 0x8cec) {
                ret = request_irq(it->options[1], das6402_interrupt, 0,
                                  dev->board_name, dev);
                if (ret == 0) {