Merge: hwmon: (w83791d) Fix NULL pointer dereference by removing unnecessary structure field

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/4344

JIRA: https://issues.redhat.com/browse/RHEL-37717  
CVE: CVE-2021-47386  
  
Build Info:  https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=61499181  
Tested: Did sanity boot testing Intel (intel-arrowlake-s-02) system.  
  
commit 943c15a  
Author: Nadezda Lutovinova <lutovinova@ispras.ru>  
Date:   Tue Sep 21 18:51:51 2021 +0300  
  
    hwmon: (w83791d) Fix NULL pointer dereference by removing unnecessary structure field  
  
    If driver read val value sufficient for  
    (val & 0x08) && (!(val & 0x80)) && ((val & 0x7) == ((val >> 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: Nadezda Lutovinova <lutovinova@ispras.ru>  
    Link: https://lore.kernel.org/r/20210921155153.28098-1-lutovinova@ispras.ru  
    [groeck: Dropped unnecessary continuation lines, fixed multi-line alignment]  
    Signed-off-by: Guenter Roeck <linux@roeck-us.net>  
  
Signed-off-by: Steve Best <sbest@redhat.com>

Approved-by: David Arcari <darcari@redhat.com>
Approved-by: Tony Camuso <tcamuso@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Lucas Zampieri <lzampier@redhat.com>

Author: zampierilucas

drivers/hwmon/w83791d.c

@@ -273,9 +273,6 @@ struct w83791d_data {
 	bool valid;			/* true if following fields are valid */
 	unsigned long last_updated;	/* In jiffies */
 
-	/* array of 2 pointers to subclients */
-	struct i2c_client *lm75[2];
-
 	/* volts */
 	u8 in[NUMBER_OF_VIN];		/* Register value */
 	u8 in_max[NUMBER_OF_VIN];	/* Register value */
@@ -1257,7 +1254,6 @@ static const struct attribute_group w83791d_group_fanpwm45 = {
 static int w83791d_detect_subclients(struct i2c_client *client)
 {
 	struct i2c_adapter *adapter = client->adapter;
-	struct w83791d_data *data = i2c_get_clientdata(client);
 	int address = client->addr;
 	int i, id;
 	u8 val;
@@ -1280,22 +1276,19 @@ static int w83791d_detect_subclients(struct i2c_client *client)
 	}
 
 	val = w83791d_read(client, W83791D_REG_I2C_SUBADDR);
-	if (!(val & 0x08))
-		data->lm75[0] = devm_i2c_new_dummy_device(&client->dev, adapter,
-							  0x48 + (val & 0x7));
-	if (!(val & 0x80)) {
-		if (!IS_ERR(data->lm75[0]) &&
-				((val & 0x7) == ((val >> 4) & 0x7))) {
-			dev_err(&client->dev,
-				"duplicate addresses 0x%x, "
-				"use force_subclient\n",
-				data->lm75[0]->addr);
-			return -ENODEV;
-		}
-		data->lm75[1] = devm_i2c_new_dummy_device(&client->dev, adapter,
-							  0x48 + ((val >> 4) & 0x7));
+
+	if (!(val & 0x88) && (val & 0x7) == ((val >> 4) & 0x7)) {
+		dev_err(&client->dev,
+			"duplicate addresses 0x%x, use force_subclient\n", 0x48 + (val & 0x7));
+		return -ENODEV;
 	}
 
+	if (!(val & 0x08))
+		devm_i2c_new_dummy_device(&client->dev, adapter, 0x48 + (val & 0x7));
+
+	if (!(val & 0x80))
+		devm_i2c_new_dummy_device(&client->dev, adapter, 0x48 + ((val >> 4) & 0x7));
+
 	return 0;
 }