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SubjectRe: [PATCH] iio: cm36651: Fix i2c client leak and possible NULL pointer dereference
On 06/03/14 09:33, Krzysztof Kozlowski wrote:
> During probe the driver allocates dummy I2C devices (i2c_new_dummy())
> but they aren't unregistered during driver remove or probe failure.
>
> Additionally driver does not check the return value of i2c_new_dummy().
> In case of error (i2c_new_device(): memory allocation failure or I2C
> address cannot be used) this function returns NULL which is later
> dereferenced by i2c_smbus_{read,write}_data() functions.
>
> Fix issues by properly checking for i2c_new_dummy() return value and
> unregistering I2C devices on driver remove or probe failure.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Good catch, but the error path needs more care.
> ---
> drivers/iio/light/cm36651.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/iio/light/cm36651.c b/drivers/iio/light/cm36651.c
> index a45e07492db3..e7e9a597159f 100644
> --- a/drivers/iio/light/cm36651.c
> +++ b/drivers/iio/light/cm36651.c
> @@ -653,6 +653,11 @@ static int cm36651_probe(struct i2c_client *client,
> cm36651->ps_client = i2c_new_dummy(client->adapter,
> CM36651_I2C_ADDR_PS);
> cm36651->ara_client = i2c_new_dummy(client->adapter, CM36651_ARA);
> + if (!cm36651->ps_client || !cm36651->ara_client) {
> + dev_err(&client->dev, "%s: new i2c device failed\n", __func__);
> + ret = -ENODEV;
> + goto error_i2c_unregister;
> + }
The two failures need to be handled independently as we only want to unregister
those that succeeded. i2c_new_dummy will not return an error and leave a device
registered. This is particularly true given the first thing that i2c_unregister_device
does is to derefence the client pointer. That will cause a segfault if you do it
for NULL as here.

> mutex_init(&cm36651->lock);
> indio_dev->dev.parent = &client->dev;
> indio_dev->channels = cm36651_channels;
> @@ -687,6 +692,11 @@ error_free_irq:
> free_irq(client->irq, indio_dev);
> error_disable_reg:
> regulator_disable(cm36651->vled_reg);
> +error_i2c_unregister:
> + if (cm36651->ps_client)
> + i2c_unregister_device(cm36651->ps_client);
> + if (cm36651->ara_client)
> + i2c_unregister_device(cm36651->ara_client);
> return ret;
> }
>
> @@ -698,6 +708,8 @@ static int cm36651_remove(struct i2c_client *client)
> iio_device_unregister(indio_dev);
> regulator_disable(cm36651->vled_reg);
> free_irq(client->irq, indio_dev);
> + i2c_unregister_device(cm36651->ps_client);
> + i2c_unregister_device(cm36651->ara_client);
Good catch.
>
> return 0;
> }
>



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