linux-kernel - [PATCH] mfd: menelaus: fix possible race condition and leak

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Date:   Sun,  9 Sep 2018 22:48:58 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Tony Lindgren <tony@...mide.com>, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: [PATCH] mfd: menelaus: fix possible race condition and leak

The IRQ work is added before the struct rtc is allocated and registered,
but this struct is used in the IRQ handler. This may lead to a NULL pointer
dereference.

Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
before calling menelaus_add_irq_work.

Also, this solves a possible leak as the RTC is never released.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
---

Lee,

If that is ok with you, I would like to take this patch through the RTC
tree. So I can have a follow up patch removing rtc_device_register().

Thanks

 drivers/mfd/menelaus.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/mfd/menelaus.c b/drivers/mfd/menelaus.c
index 29b7164a823b..d28ebe7ecd21 100644
--- a/drivers/mfd/menelaus.c
+++ b/drivers/mfd/menelaus.c
@@ -1094,6 +1094,7 @@ static void menelaus_rtc_alarm_work(struct menelaus_chip *m)
 static inline void menelaus_rtc_init(struct menelaus_chip *m)
 {
 	int	alarm = (m->client->irq > 0);
+	int	err;
 
 	/* assume 32KDETEN pin is pulled high */
 	if (!(menelaus_read_reg(MENELAUS_OSC_CTRL) & 0x80)) {
@@ -1101,6 +1102,12 @@ static inline void menelaus_rtc_init(struct menelaus_chip *m)
 		return;
 	}
 
+	m->rtc = devm_rtc_allocate_device(&m->client->dev);
+	if (IS_ERR(m->rtc))
+		return;
+
+	m->rtc->ops = &menelaus_rtc_ops;
+
 	/* support RTC alarm; it can issue wakeups */
 	if (alarm) {
 		if (menelaus_add_irq_work(MENELAUS_RTCALM_IRQ,
@@ -1125,10 +1132,8 @@ static inline void menelaus_rtc_init(struct menelaus_chip *m)
 		menelaus_write_reg(MENELAUS_RTC_CTRL, m->rtc_control);
 	}
 
-	m->rtc = rtc_device_register(DRIVER_NAME,
-			&m->client->dev,
-			&menelaus_rtc_ops, THIS_MODULE);
-	if (IS_ERR(m->rtc)) {
+	err = rtc_register_device(m->rtc);
+	if (err) {
 		if (alarm) {
 			menelaus_remove_irq_work(MENELAUS_RTCALM_IRQ);
 			device_init_wakeup(&m->client->dev, 0);
-- 
2.19.0.rc2