linux-kernel - [PATCH V3 REPOST] comedi: pcl726: Prevent invalid irq number

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Message-ID: <20250724110754.8708-1-abbotti@mev.co.uk>
Date: Thu, 24 Jul 2025 12:07:36 +0100
From: Ian Abbott <abbotti@....co.uk>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Edward Adam Davis <eadavis@...com>,
	syzkaller-bugs@...glegroups.com,
	stable@...r.kernel.org,
	syzbot+5cd373521edd68bebcb3@...kaller.appspotmail.com,
	Ian Abbott <abbotti@....co.uk>
Subject: [PATCH V3 REPOST] comedi: pcl726: Prevent invalid irq number

From: Edward Adam Davis <eadavis@...com>

The reproducer passed in an irq number(0x80008000) that was too large,
which triggered the oob.

Added an interrupt number check to prevent users from passing in an irq
number that was too large.

If `it->options[1]` is 31, then `1 << it->options[1]` is still invalid
because it shifts a 1-bit into the sign bit (which is UB in C).
Possible solutions include reducing the upper bound on the
`it->options[1]` value to 30 or lower, or using `1U << it->options[1]`.

The old code would just not attempt to request the IRQ if the
`options[1]` value were invalid.  And it would still configure the
device without interrupts even if the call to `request_irq` returned an
error.  So it would be better to combine this test with the test below.

Fixes: fff46207245c ("staging: comedi: pcl726: enable the interrupt support code")
Cc: <stable@...r.kernel.org> # 5.13+
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Reported-by: syzbot+5cd373521edd68bebcb3@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5cd373521edd68bebcb3
Tested-by: syzbot+5cd373521edd68bebcb3@...kaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@...com>
Reviewed-by: Ian Abbott <abbotti@....co.uk>
---
 drivers/comedi/drivers/pcl726.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/comedi/drivers/pcl726.c b/drivers/comedi/drivers/pcl726.c
index 0430630e6ebb..b542896fa0e4 100644
--- a/drivers/comedi/drivers/pcl726.c
+++ b/drivers/comedi/drivers/pcl726.c
@@ -328,7 +328,8 @@ static int pcl726_attach(struct comedi_device *dev,
 	 * Hook up the external trigger source interrupt only if the
 	 * user config option is valid and the board supports interrupts.
 	 */
-	if (it->options[1] && (board->irq_mask & (1 << it->options[1]))) {
+	if (it->options[1] > 0 && it->options[1] < 16 &&
+	    (board->irq_mask & (1U << it->options[1]))) {
 		ret = request_irq(it->options[1], pcl726_interrupt, 0,
 				  dev->board_name, dev);
 		if (ret == 0) {
-- 
2.47.2