[PATCH 5.14 041/172] hwmon: (w83793) Fix NULL pointer dereference by removing unnecessary structure field

Greg Kroah-Hartman
2021-10-04T13:30:19Z

From: Nadezda Lutovinova <lutovinova@ispras.ru>

commit dd4d747ef05addab887dc8ff0d6ab9860bbcd783 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: Nadezda 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: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/hwmon/w83793.c | 26 +++++++++++---------------
1 file changed, 11 insertions(+), 15 deletions(-)

--- a/drivers/hwmon/w83793.c
+++ b/drivers/hwmon/w83793.c
@@ -202,7 +202,6 @@ static inline s8 TEMP_TO_REG(long val, s
}

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_clie
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_clie
}

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;
}