[PATCH 5.4.y] comedi: das6402: Fix bit shift out of bounds

[PATCH 5.4.y] comedi: das6402: Fix bit shift out of bounds

[Ian Abbott]

[ Upstream commit 70f2b28b5243df557f51c054c20058ae207baaac ]

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>
---
 drivers/staging/comedi/drivers/das6402.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/das6402.c b/drivers/staging/comedi/drivers/das6402.c
index 0034005bdf8f..0cd5d1b1ffde 100644
--- a/drivers/staging/comedi/drivers/das6402.c
+++ b/drivers/staging/comedi/drivers/das6402.c
@@ -569,7 +569,8 @@ 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) {
-- 
2.47.2

Re: [PATCH 5.4.y] comedi: das6402: 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: 70f2b28b5243df557f51c054c20058ae207baaac

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:  70f2b28b5243 ! 1:  e24d1f87963a comedi: das6402: Fix bit shift out of bounds
    @@ Metadata
      ## Commit message ##
         comedi: das6402: Fix bit shift out of bounds
     
    +    [ Upstream commit 70f2b28b5243df557f51c054c20058ae207baaac ]
    +
         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 */
    @@ Commit message
         Link: https://lore.kernel.org/r/20250707135737.77448-1-abbotti@mev.co.uk
         Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
     
    - ## drivers/comedi/drivers/das6402.c ##
    -@@ drivers/comedi/drivers/das6402.c: static int das6402_attach(struct comedi_device *dev,
    + ## drivers/staging/comedi/drivers/das6402.c ##
    +@@ drivers/staging/comedi/drivers/das6402.c: 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 */

---

Results of testing on various branches:

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