comedi: das16m1: Fix bit shift out of bounds

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

	/* only irqs 2, 3, 4, 5, 6, 7, 10, 11, 12, 14, and 15 are valid */
	if ((1 << it->options[1]) & 0xdcfc) {

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.

Reported-by: syzbot+c52293513298e0fd9a94@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c52293513298e0fd9a94
Fixes: 729988507680 ("staging: comedi: das16m1: tidy up the irq support in das16m1_attach()")
Tested-by: syzbot+c52293513298e0fd9a94@syzkaller.appspotmail.com
Suggested-by: "Enju, Kohei" <enjuk@amazon.co.jp>
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250707130908.70758-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/comedi/drivers/das16m1.c b/drivers/comedi/drivers/das16m1.c
index b8ea737ad3d14cbb7cf6d19dbf5823e203d4b5d6..1b638f5b5a4fb9d17f82d5568bd7df84b88a7f4f 100644 (file)
--- a/drivers/comedi/drivers/das16m1.c
+++ b/drivers/comedi/drivers/das16m1.c
@@ -522,7 +522,8 @@ static int das16m1_attach(struct comedi_device *dev,
        devpriv->extra_iobase = dev->iobase + DAS16M1_8255_IOBASE;
 
        /* only irqs 2, 3, 4, 5, 6, 7, 10, 11, 12, 14, and 15 are valid */
-       if ((1 << it->options[1]) & 0xdcfc) {
+       if (it->options[1] >= 2 && it->options[1] <= 15 &&
+           (1 << it->options[1]) & 0xdcfc) {
                ret = request_irq(it->options[1], das16m1_interrupt, 0,
                                  dev->board_name, dev);
                if (ret == 0)