2021-08-11 16:19:40

by Nadezda Lutovinova

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

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 <[email protected]>
---
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


2021-08-11 18:24:16

by Guenter Roeck

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

On Wed, Aug 11, 2021 at 07:15:15PM +0300, Nadezda Lutovinova wrote:
> 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).
>

One patch per driver, please.

> Signed-off-by: Nadezda Lutovinova <[email protected]>
> ---
> 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, "

As you pointed out in te other e-mail, lm75[] does not really serve
a purpose anymore. It might be much better to replace this code with
something like

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;
}

Same for the other chips.

Guenter

> 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
>

2021-09-21 15:55:38

by Nadezda Lutovinova

[permalink] [raw]
Subject: [PATCH v2 1/3] 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).

Signed-off-by: Nadezda Lutovinova <[email protected]>
---
v2:
- split one file per patch
- remove lm75[] instead of adding checking
---
drivers/hwmon/w83791d.c | 32 ++++++++++++++------------------
1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c
index 37b25a1474c4..b4eae45859c1 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;
@@ -1280,21 +1276,21 @@ static int w83791d_detect_subclients(struct i2c_client *client)
}

val = w83791d_read(client, W83791D_REG_I2C_SUBADDR);
+
+ 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))
- 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));
- }
+ 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;
}
--
2.17.1

2021-09-21 15:56:05

by Nadezda Lutovinova

[permalink] [raw]
Subject: [PATCH v2 2/3] hwmon: (w83792d) 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).

Signed-off-by: Nadezda Lutovinova <[email protected]>
---
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;
}
--
2.17.1

2021-09-21 15:56:13

by Nadezda Lutovinova

[permalink] [raw]
Subject: [PATCH v2 3/3] hwmon: (w83793) Fix NULL pointer dereference by removing unnecessary structure field

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 <[email protected]>
---
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;
}
--
2.17.1

2021-10-02 12:10:15

by Guenter Roeck

[permalink] [raw]
Subject: Re: [PATCH v2 1/3] hwmon: (w83791d) Fix NULL pointer dereference by removing unnecessary structure field

On Tue, Sep 21, 2021 at 06:51:51PM +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 <[email protected]>

Applied, after fixing multi-line alignments.

Guenter

> ---
> v2:
> - split one file per patch
> - remove lm75[] instead of adding checking
> ---
> drivers/hwmon/w83791d.c | 32 ++++++++++++++------------------
> 1 file changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/hwmon/w83791d.c b/drivers/hwmon/w83791d.c
> index 37b25a1474c4..b4eae45859c1 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;
> @@ -1280,21 +1276,21 @@ static int w83791d_detect_subclients(struct i2c_client *client)
> }
>
> val = w83791d_read(client, W83791D_REG_I2C_SUBADDR);
> +
> + 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))
> - 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));
> - }
> + 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;
> }

2021-10-02 12:20:09

by Guenter Roeck

[permalink] [raw]
Subject: Re: [PATCH v2 3/3] hwmon: (w83793) Fix NULL pointer dereference by removing unnecessary structure field

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 <[email protected]>

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;
> }

2021-10-02 12:50:50

by Guenter Roeck

[permalink] [raw]
Subject: Re: [PATCH v2 2/3] hwmon: (w83792d) Fix NULL pointer dereference by removing unnecessary structure field

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 <[email protected]>

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;
> }