From 3ab8c5ed4f84fa20cd16794fe8dc31f633fbc70c Mon Sep 17 00:00:00 2001
From: Oleksij Rempel <o.rempel@pengutronix.de>
Date: Wed, 18 Dec 2024 20:34:58 +0100
Subject: [PATCH] rtc: pcf85063: fix potential OOB write in PCF85063 NVMEM read
The nvmem interface supports variable buffer sizes, while the regmap
interface operates with fixed-size storage. If an nvmem client uses a
buffer size less than 4 bytes, regmap_read will write out of bounds
as it expects the buffer to point at an unsigned int.
Fix this by using an intermediary unsigned int to hold the value.
Fixes: fadfd092ee91 ("rtc: pcf85063: add nvram support")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.kernel.org/r/20241218-rtc-pcf85063-stack-corruption-v1-1-12fd0ee0f046@pengutronix.de
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
drivers/rtc/rtc-pcf85063.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/rtc/rtc-pcf85063.c b/drivers/rtc/rtc-pcf85063.c
index fdbc07f14036a..905986c616559 100644
--- a/drivers/rtc/rtc-pcf85063.c
+++ b/drivers/rtc/rtc-pcf85063.c
@@ -322,7 +322,16 @@ static const struct rtc_class_ops pcf85063_rtc_ops = {
static int pcf85063_nvmem_read(void *priv, unsigned int offset,
void *val, size_t bytes)
{
- return regmap_read(priv, PCF85063_REG_RAM, val);
+ unsigned int tmp;
+ int ret;
+
+ ret = regmap_read(priv, PCF85063_REG_RAM, &tmp);
+ if (ret < 0)
+ return ret;
+
+ *(u8 *)val = tmp;
+
+ return 0;
}
static int pcf85063_nvmem_write(void *priv, unsigned int offset,