linux-kernel - [syzbot] [comedi?] INFO: task hung in comedi

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Message-ID: <20251020175911.150815-1-n.zhandarovich@fintech.ru>
Date: Mon, 20 Oct 2025 20:59:10 +0300
From: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
To: <syzbot+7811bb68a317954a0347@...kaller.appspotmail.com>
CC: Nikita Zhandarovich <n.zhandarovich@...tech.ru>,
	<syzkaller-bugs@...glegroups.com>, <linux-kernel@...r.kernel.org>
Subject: [syzbot] [comedi?] INFO: task hung in comedi_open

#syz test

---
 drivers/comedi/drivers/multiq3.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/comedi/drivers/multiq3.c b/drivers/comedi/drivers/multiq3.c
index 467587b0b250..dc27651e0ace 100644
--- a/drivers/comedi/drivers/multiq3.c
+++ b/drivers/comedi/drivers/multiq3.c
@@ -67,6 +67,11 @@
 #define MULTIQ3_TRSFRCNTR_OL		0x10	/* xfer CNTR to OL (x and y) */
 #define MULTIQ3_EFLAG_RESET		0x06	/* reset E bit of flag reg */
 
+/*
+ * Semi-arbitrary limit on the number of optional encoder chips
+ */
+#define MULTIQ3_MAX_ENC_CHIPS		16
+
 static void multiq3_set_ctrl(struct comedi_device *dev, unsigned int bits)
 {
 	/*
@@ -314,6 +319,11 @@ static int multiq3_attach(struct comedi_device *dev,
 
 	/* Encoder (Counter) subdevice */
 	s = &dev->subdevices[4];
+
+	/* sanity check for number of optional encoders */
+	if (it->options[2] > MULTIQ3_MAX_ENC_CHIPS)
+		it->options[2] = MULTIQ3_MAX_ENC_CHIPS;
+
 	s->type		= COMEDI_SUBD_COUNTER;
 	s->subdev_flags	= SDF_READABLE | SDF_LSAMPL;
 	s->n_chan	= it->options[2] * 2;