On Tue, Sep 21, 2021 at 06:51:53PM +0300, Nadezda Lutovinova wrote:
> 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).
>
> Signed-off-by: Nadezda Lutovinova <lutovinova@xxxxxxxxx>
Applied, after fixing multi-line alignments
Thanks,
Guenter
> ---
> v2:
> - split one file per patch
> - remove lm75[] instead of adding checking
> ---
> drivers/hwmon/w83793.c | 29 ++++++++++++++---------------
> 1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/hwmon/w83793.c b/drivers/hwmon/w83793.c
> index e7d0484eabe4..4ee96756ed49 100644
> --- a/drivers/hwmon/w83793.c
> +++ b/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) {
> @@ -1586,20 +1584,21 @@ w83793_detect_subclients(struct i2c_client *client)
> }
>
> tmp = w83793_read_value(client, W83793_REG_I2C_SUBADDR);
> +
> + 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))
> - 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));
> - }
> + 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;
> }
