linux-kernel - [PATCH] power: supply: max17042_battery: fix some usage of uninitialized variables

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Message-Id: <20191002155547.9137-1-yzhai003@ucr.edu>
Date:   Wed,  2 Oct 2019 08:55:47 -0700
From:   Yizhuo <yzhai003@....edu>
To:     unlisted-recipients:; (no To-header on input)
Cc:     csong@...ucr.edu, zhiyunq@...ucr.edu, Yizhuo <yzhai003@....edu>,
        Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] power: supply: max17042_battery: fix some usage of uninitialized variables

Several functions in this file are trying to use regmap_read() to
initialize the specific variable, however, if regmap_read() fails,
the variable could be uninitialized but used directly, which is
potentially unsafe. The return value of regmap_read() should be
checked and handled. The same case also happens in function
max17042_thread_handler() but it needs more effort to patch.

Signed-off-by: Yizhuo <yzhai003@....edu>
---
 drivers/power/supply/max17042_battery.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/power/supply/max17042_battery.c b/drivers/power/supply/max17042_battery.c
index e6a2dacaa730..8e5727010ed2 100644
--- a/drivers/power/supply/max17042_battery.c
+++ b/drivers/power/supply/max17042_battery.c
@@ -675,8 +675,12 @@ static void max17042_reset_vfsoc0_reg(struct max17042_chip *chip)
 {
 	unsigned int vfSoc;
 	struct regmap *map = chip->regmap;
+	int ret;
+
+	ret = regmap_read(map, MAX17042_VFSOC, &vfSoc);
+	if (ret)
+		return;
 
-	regmap_read(map, MAX17042_VFSOC, &vfSoc);
 	regmap_write(map, MAX17042_VFSOC0Enable, VFSOC0_UNLOCK);
 	max17042_write_verify_reg(map, MAX17042_VFSOC0, vfSoc);
 	regmap_write(map, MAX17042_VFSOC0Enable, VFSOC0_LOCK);
@@ -686,12 +690,18 @@ static void max17042_load_new_capacity_params(struct max17042_chip *chip)
 {
 	u32 full_cap0, rep_cap, dq_acc, vfSoc;
 	u32 rem_cap;
+	int ret;
 
 	struct max17042_config_data *config = chip->pdata->config_data;
 	struct regmap *map = chip->regmap;
 
-	regmap_read(map, MAX17042_FullCAP0, &full_cap0);
-	regmap_read(map, MAX17042_VFSOC, &vfSoc);
+	ret = regmap_read(map, MAX17042_FullCAP0, &full_cap0);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(map, MAX17042_VFSOC, &vfSoc);
+	if (ret)
+		return ret;
 
 	/* fg_vfSoc needs to shifted by 8 bits to get the
 	 * perc in 1% accuracy, to get the right rem_cap multiply
@@ -1108,7 +1118,12 @@ static int max17042_probe(struct i2c_client *client,
 	if (!client->irq)
 		regmap_write(chip->regmap, MAX17042_SALRT_Th, 0xff00);
 
-	regmap_read(chip->regmap, MAX17042_STATUS, &val);
+	ret = regmap_read(chip->regmap, MAX17042_STATUS, &val);
+	if (ret) {
+		dev_err(&client->dev, "Failed to get MAX17042_STATUS.\n");
+		return ret;
+	}
+
 	if (val & STATUS_POR_BIT) {
 		INIT_WORK(&chip->work, max17042_init_worker);
 		ret = devm_add_action(&client->dev, max17042_stop_work, chip);
-- 
2.17.1