linux-kernel - [PATCH AUTOSEL 5.15 03/27] rtc: pcf2127: fix bug when reading alarm registers

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Date:   Wed,  6 Apr 2022 21:12:33 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hugo Villeneuve <hvilleneuve@...onoff.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Sasha Levin <sashal@...nel.org>, a.zummo@...ertech.it,
        linux-rtc@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 03/27] rtc: pcf2127: fix bug when reading alarm registers

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

[ Upstream commit 73ce05302007eece23a6acb7dc124c92a2209087 ]

The first bug is that reading the 5 alarm registers results in a read
operation of 20 bytes. The reason is because the destination buffer is
defined as an array of "unsigned int", and we use the sizeof()
operator on this array to define the bulk read count.

The second bug is that the read value is invalid, because we are
indexing the destination buffer as integers (4 bytes), instead of
indexing it as u8.

Changing the destination buffer type to u8 fixes both problems.

Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
Link: https://lore.kernel.org/r/20220208162908.3182581-1-hugo@hugovil.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/rtc/rtc-pcf2127.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
index 56c58b055dff..43f801107095 100644
--- a/drivers/rtc/rtc-pcf2127.c
+++ b/drivers/rtc/rtc-pcf2127.c
@@ -374,7 +374,8 @@ static int pcf2127_watchdog_init(struct device *dev, struct pcf2127 *pcf2127)
 static int pcf2127_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
 	struct pcf2127 *pcf2127 = dev_get_drvdata(dev);
-	unsigned int buf[5], ctrl2;
+	u8 buf[5];
+	unsigned int ctrl2;
 	int ret;
 
 	ret = regmap_read(pcf2127->regmap, PCF2127_REG_CTRL2, &ctrl2);
-- 
2.35.1