hwmon: (w83793) Fix NULL pointer dereference by removing unnecessary structure field

stable inclusion
from stable-5.10.71
commit 7c4fd5de39f273626a2b0f3a446d2cc85cd47616
bugzilla: 182981 https://gitee.com/openeuler/kernel/issues/I4I3KD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7c4fd5de39f273626a2b0f3a446d2cc85cd47616

--------------------------------

commit dd4d747e upstream.

If driver read tmp value sufficient for
(tmp & 0x08) && (!(tmp & 0x80)) && ((tmp & 0x7) == ((tmp >> 4) & 0x7))
from device then Null pointer dereference occurs.
(It is possible if tmp = 0b0xyz1xyz, where same literals mean same numbers)
Also lm75[] does not serve a purpose anymore after switching to
devm_i2c_new_dummy_device() in w83791d_detect_subclients().

The patch fixes possible NULL pointer dereference by removing lm75[].

Found by Linux Driver Verification project (linuxtesting.org).

Cc: stable@vger.kernel.org
Signed-off-by: NNadezda Lutovinova <lutovinova@ispras.ru>
Link: https://lore.kernel.org/r/20210921155153.28098-3-lutovinova@ispras.ru
[groeck: Dropped unnecessary continuation lines, fixed multi-line alignments]
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/hwmon/w83793.c

@@ -202,7 +202,6 @@ static inline s8 TEMP_TO_REG(long val, s8 min, s8 max)
 }
 
 struct w83793_data {
-	struct i2c_client *lm75[2];
 	struct device *hwmon_dev;
 	struct mutex update_lock;
 	char valid;			/* !=0 if following fields are valid */
@@ -1566,7 +1565,6 @@ w83793_detect_subclients(struct i2c_client *client)
 	int address = client->addr;
 	u8 tmp;
 	struct i2c_adapter *adapter = client->adapter;
-	struct w83793_data *data = i2c_get_clientdata(client);
 
 	id = i2c_adapter_id(adapter);
 	if (force_subclients[0] == id && force_subclients[1] == address) {
@@ -1586,21 +1584,19 @@ w83793_detect_subclients(struct i2c_client *client)
 	}
 
 	tmp = w83793_read_value(client, W83793_REG_I2C_SUBADDR);
-	if (!(tmp & 0x08))
-		data->lm75[0] = devm_i2c_new_dummy_device(&client->dev, adapter,
-							  0x48 + (tmp & 0x7));
-	if (!(tmp & 0x80)) {
-		if (!IS_ERR(data->lm75[0])
-		    && ((tmp & 0x7) == ((tmp >> 4) & 0x7))) {
-			dev_err(&client->dev,
-				"duplicate addresses 0x%x, "
-				"use force_subclients\n", data->lm75[0]->addr);
-			return -ENODEV;
-		}
-		data->lm75[1] = devm_i2c_new_dummy_device(&client->dev, adapter,
-							  0x48 + ((tmp >> 4) & 0x7));
+
+	if (!(tmp & 0x88) && (tmp & 0x7) == ((tmp >> 4) & 0x7)) {
+		dev_err(&client->dev,
+			"duplicate addresses 0x%x, use force_subclient\n", 0x48 + (tmp & 0x7));
+		return -ENODEV;
 	}
 
+	if (!(tmp & 0x08))
+		devm_i2c_new_dummy_device(&client->dev, adapter, 0x48 + (tmp & 0x7));
+
+	if (!(tmp & 0x80))
+		devm_i2c_new_dummy_device(&client->dev, adapter, 0x48 + ((tmp >> 4) & 0x7));
+
 	return 0;
 }