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 --- Patch does not apply cleanly to longterm kernels 5.4.x and 5.10.x. --- drivers/comedi/drivers/das16m1.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/das16m1.c b/drivers/comedi/drivers/das16m1.c index b8ea737ad3d1..1b638f5b5a4f 100644 --- 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)