[PATCH 5.4.y] comedi: das16m1: Fix bit shift out of bounds

[PATCH 5.4.y] comedi: das16m1: Fix bit shift out of bounds

[Ian Abbott]

[ Upstream commit ed93c6f68a3be06e4e0c331c6e751f462dee3932 ]

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>
---
 drivers/staging/comedi/drivers/das16m1.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/das16m1.c b/drivers/staging/comedi/drivers/das16m1.c
index 4e36377b592a..16e4c1637d0b 100644
--- a/drivers/staging/comedi/drivers/das16m1.c
+++ b/drivers/staging/comedi/drivers/das16m1.c
@@ -523,7 +523,8 @@ 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)
-- 
2.47.2

Re: [PATCH 5.4.y] comedi: das16m1: Fix bit shift out of bounds

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: ed93c6f68a3be06e4e0c331c6e751f462dee3932

Status in newer kernel trees:
6.15.y | Not found
6.12.y | Not found
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found
5.10.y | Not found

Note: The patch differs from the upstream commit:
---
1:  ed93c6f68a3b ! 1:  05de6bb6adee comedi: das16m1: Fix bit shift out of bounds
    @@ Metadata
      ## Commit message ##
         comedi: das16m1: Fix bit shift out of bounds
     
    +    [ Upstream commit ed93c6f68a3be06e4e0c331c6e751f462dee3932 ]
    +
         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 */
    @@ Commit message
         Link: https://lore.kernel.org/r/20250707130908.70758-1-abbotti@mev.co.uk
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     
    - ## drivers/comedi/drivers/das16m1.c ##
    -@@ drivers/comedi/drivers/das16m1.c: static int das16m1_attach(struct comedi_device *dev,
    + ## drivers/staging/comedi/drivers/das16m1.c ##
    +@@ drivers/staging/comedi/drivers/das16m1.c: 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 */

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| origin/linux-5.4.y        | Success     | Success    |