The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 943c15ac1b84d378da26bba41c83c67e16499ac4 Mon Sep 17 00:00:00 2001

From: Nadezda Lutovinova lutovinova@ispras.ru Date: Tue, 21 Sep 2021 18:51:51 +0300 Subject: [PATCH] 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

diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c index 37b25a1474c4..3c1be2c11fdf 100644 --- a/drivers/hwmon/w83791d.c +++ b/drivers/hwmon/w83791d.c @@ -273,9 +273,6 @@ struct w83791d_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]; - /* 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; }