[PATCH] hwmon: Correct the error handling in w83793.c, w83791d.c, w83792d.c

[Nadezda Lutovinova]

If driver read tmp (or val) 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)

The patch adds checking if data->lm75[0] is NULL.

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

Signed-off-by: Nadezda Lutovinova <lutovinova@xxxxxxxxx>
---
 drivers/hwmon/w83791d.c | 2 +-
 drivers/hwmon/w83792d.c | 2 +-
 drivers/hwmon/w83793.c  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c
index 37b25a1474c4..8b30bbfafaa7 100644
--- a/drivers/hwmon/w83791d.c
+++ b/drivers/hwmon/w83791d.c
@@ -1284,7 +1284,7 @@ static int w83791d_detect_subclients(struct i2c_client *client)
 		data->lm75[0] = devm_i2c_new_dummy_device(&client->dev, adapter,
 							  0x48 + (val & 0x7));
 	if (!(val & 0x80)) {
-		if (!IS_ERR(data->lm75[0]) &&
+		if (!IS_ERR_OR_NULL(data->lm75[0]) &&
 				((val & 0x7) == ((val >> 4) & 0x7))) {
 			dev_err(&client->dev,
 				"duplicate addresses 0x%x, "
diff --git a/drivers/hwmon/w83792d.c b/drivers/hwmon/w83792d.c
index abd5c3a722b9..85ae12d950e1 100644
--- a/drivers/hwmon/w83792d.c
+++ b/drivers/hwmon/w83792d.c
@@ -950,7 +950,7 @@ w83792d_detect_subclients(struct i2c_client *new_client)
 		data->lm75[0] = devm_i2c_new_dummy_device(&new_client->dev, adapter,
 							  0x48 + (val & 0x7));
 	if (!(val & 0x80)) {
-		if (!IS_ERR(data->lm75[0]) &&
+		if (!IS_ERR_OR_NULL(data->lm75[0]) &&
 			((val & 0x7) == ((val >> 4) & 0x7))) {
 			dev_err(&new_client->dev,
 				"duplicate addresses 0x%x, use force_subclient\n",
diff --git a/drivers/hwmon/w83793.c b/drivers/hwmon/w83793.c
index e7d0484eabe4..9d8c44e2fa6e 100644
--- a/drivers/hwmon/w83793.c
+++ b/drivers/hwmon/w83793.c
@@ -1590,7 +1590,7 @@ w83793_detect_subclients(struct i2c_client *client)
 		data->lm75[0] = devm_i2c_new_dummy_device(&client->dev, adapter,
 							  0x48 + (tmp & 0x7));
 	if (!(tmp & 0x80)) {
-		if (!IS_ERR(data->lm75[0])
+		if (!IS_ERR_OR_NULL(data->lm75[0])
 		    && ((tmp & 0x7) == ((tmp >> 4) & 0x7))) {
 			dev_err(&client->dev,
 				"duplicate addresses 0x%x, "
-- 
2.17.1