On Tue, Sep 21, 2021 at 06:51:52PM +0300, Nadezda Lutovinova wrote:
> 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).
>
> Signed-off-by: Nadezda Lutovinova <lutovinova@xxxxxxxxx>
Applied, after fixing multi-line alignments
> ---
> v2:
> - split one file per patch
> - remove lm75[] instead of adding checking
> ---
> drivers/hwmon/w83792d.c | 31 ++++++++++++++-----------------
> 1 file changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/hwmon/w83792d.c b/drivers/hwmon/w83792d.c
> index abd5c3a722b9..8a72be4ad74f 100644
> --- a/drivers/hwmon/w83792d.c
> +++ b/drivers/hwmon/w83792d.c
> @@ -264,9 +264,6 @@ struct w83792d_data {
> char valid; /* !=0 if following fields are valid */
> unsigned long last_updated; /* In jiffies */
>
> - /* array of 2 pointers to subclients */
> - struct i2c_client *lm75[2];
> -
> u8 in[9]; /* Register value */
> u8 in_max[9]; /* Register value */
> u8 in_min[9]; /* Register value */
> @@ -927,7 +924,6 @@ w83792d_detect_subclients(struct i2c_client *new_client)
> int address = new_client->addr;
> u8 val;
> struct i2c_adapter *adapter = new_client->adapter;
> - struct w83792d_data *data = i2c_get_clientdata(new_client);
>
> id = i2c_adapter_id(adapter);
> if (force_subclients[0] == id && force_subclients[1] == address) {
> @@ -946,20 +942,21 @@ w83792d_detect_subclients(struct i2c_client *new_client)
> }
>
> val = w83792d_read_value(new_client, W83792D_REG_I2C_SUBADDR);
> +
> + if (!(val & 0x88) && (val & 0x7) == ((val >> 4) & 0x7)) {
> + dev_err(&new_client->dev,
> + "duplicate addresses 0x%x, use force_subclient\n",
> + 0x48 + (val & 0x7));
> + return -ENODEV;
> + }
> +
> if (!(val & 0x08))
> - data->lm75[0] = devm_i2c_new_dummy_device(&new_client->dev, adapter,
> - 0x48 + (val & 0x7));
> - if (!(val & 0x80)) {
> - if (!IS_ERR(data->lm75[0]) &&
> - ((val & 0x7) == ((val >> 4) & 0x7))) {
> - dev_err(&new_client->dev,
> - "duplicate addresses 0x%x, use force_subclient\n",
> - data->lm75[0]->addr);
> - return -ENODEV;
> - }
> - data->lm75[1] = devm_i2c_new_dummy_device(&new_client->dev, adapter,
> - 0x48 + ((val >> 4) & 0x7));
> - }
> + devm_i2c_new_dummy_device(&new_client->dev, adapter,
> + 0x48 + (val & 0x7));
> +
> + if (!(val & 0x80))
> + devm_i2c_new_dummy_device(&new_client->dev, adapter,
> + 0x48 + ((val >> 4) & 0x7));
>
> return 0;
> }
