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

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Message-ID: <20251021122436.160398-1-n.zhandarovich@fintech.ru>
Date: Tue, 21 Oct 2025 15:24:34 +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: Re: [syzbot] [comedi?] INFO: task hung in comedi_open

#syz test

---
 drivers/comedi/drivers/multiq3.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/comedi/drivers/multiq3.c b/drivers/comedi/drivers/multiq3.c
index 07ff5383da99..0248321e3bfa 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)
 {
 	/*
@@ -312,6 +317,10 @@ static int multiq3_attach(struct comedi_device *dev,
 	s->insn_read	= multiq3_encoder_insn_read;
 	s->insn_config	= multiq3_encoder_insn_config;
 
+	/* sanity check for number of optional encoders */
+	if (s->n_chan > MULTIQ3_MAX_ENC_CHIPS)
+		s->n_chan = MULTIQ3_MAX_ENC_CHIPS;
+
 	for (i = 0; i < s->n_chan; i++)
 		multiq3_encoder_reset(dev, i);