linux-kernel - [PATCH] hwmon: max31827: Fix uninitialized variable lsb_idx in max31827_init

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Message-Id: <20250410194833.21366-1-purvayeshi550@gmail.com>
Date: Fri, 11 Apr 2025 01:18:33 +0530
From: Purva Yeshi <purvayeshi550@...il.com>
To: 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: max31827: Fix uninitialized variable lsb_idx in max31827_init_client

Fix Smatch-detected issue:
drivers/hwmon/max31827.c:564 max31827_init_client() error:
uninitialized symbol 'lsb_idx'.

In the max31827_init_client() function, the variable lsb_idx is assigned
a value only when data has exactly one bit set (hweight32(data) == 1).
If this condition isn't met, lsb_idx remains uninitialized, leading to
undefined behavior when it's subsequently used.

Ensure that data is non-zero and has exactly one bit set before
calling __ffs(data) to determine lsb_idx. Additionally, verify that
lsb_idx does not exceed 4. This approach prevents the use of an
uninitialized lsb_idx and resolves the Smatch warning.

Signed-off-by: Purva Yeshi <purvayeshi550@...il.com>
---
 drivers/hwmon/max31827.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index 48e8f8ba4d05..c62eaf186d9d 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -558,10 +558,13 @@ static int max31827_init_client(struct max31827_state *st,
 		/*
 		 * Convert the desired fault queue into register bits.
 		 */
-		if (data != 0)
-			lsb_idx = __ffs(data);
+		if (data == 0 || hweight32(data) != 1) {
+			dev_err(dev, "Invalid data in adi,fault-q\n");
+			return -EINVAL;
+		}

-		if (hweight32(data) != 1 || lsb_idx > 4) {
+		lsb_idx = __ffs(data);
+		if (lsb_idx > 4) {
 			dev_err(dev, "Invalid data in adi,fault-q\n");
 			return -EINVAL;
 		}
-- 
2.34.1