linux-kernel - [PATCH] hwmon: asus_atk0110: NULL buf.pointer after free

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Message-Id: <20250410183450.15514-1-purvayeshi550@gmail.com>
Date: Fri, 11 Apr 2025 00:04:50 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: Luca Tettamanti <kronos.it@...il.com>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>
Cc: linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Purva Yeshi <purvayeshi550@...il.com>
Subject: [PATCH] hwmon: asus_atk0110: NULL buf.pointer after free

Fix Smatch-detected issue:
drivers/hwmon/asus_atk0110.c:987 atk_enumerate_old_hwmon() error:
double free of 'buf.pointer' (line 966)
drivers/hwmon/asus_atk0110.c:1008 atk_enumerate_old_hwmon() error:
double free of 'buf.pointer' (line 987)

Smatch warns about double free of 'buf.pointer'.
This happens because the same buffer struct is reused multiple times
without resetting the pointer after free. Set buf.pointer = NULL
after each ACPI_FREE to prevent possible use-after-free bugs.

Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
---
 drivers/hwmon/asus_atk0110.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hwmon/asus_atk0110.c b/drivers/hwmon/asus_atk0110.c
index c80350e499e9..83ee7f25bb8e 100644
--- a/drivers/hwmon/asus_atk0110.c
+++ b/drivers/hwmon/asus_atk0110.c
@@ -964,6 +964,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data)
 			count++;
 	}
 	ACPI_FREE(buf.pointer);
+	buf.pointer = NULL;
 
 	/* Temperatures */
 	buf.length = ACPI_ALLOCATE_BUFFER;
@@ -985,6 +986,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data)
 			count++;
 	}
 	ACPI_FREE(buf.pointer);
+	buf.pointer = NULL;
 
 	/* Fans */
 	buf.length = ACPI_ALLOCATE_BUFFER;
@@ -1006,6 +1008,7 @@ static int atk_enumerate_old_hwmon(struct atk_data *data)
 			count++;
 	}
 	ACPI_FREE(buf.pointer);
+	buf.pointer = NULL;
 
 	return count;
 }
-- 
2.34.1