Messages in this thread | | | Date | Mon, 17 Mar 2014 19:24:10 +0000 | From | Jonathan Cameron <> | Subject | Re: [PATCH] iio: cm36651: Fix i2c client leak and possible NULL pointer dereference |
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On 17/03/14 08:01, Krzysztof Kozlowski wrote: > Hi, > > On Sat, 2014-03-15 at 16:24 +0000, Jonathan Cameron wrote: >> 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. >> > > Where the segfault would occur? If i2c_new_dummy fails then > i2c_unregister_device() will be called only on NON-null values: > +error_i2c_unregister: > + if (cm36651->ps_client) > + i2c_unregister_device(cm36651->ps_client); > + if (cm36651->ara_client) > + i2c_unregister_device(cm36651->ara_client); > > If probe() succeeds (both i2c_new_dummy return proper pointer) then > remove() will unregister two i2c devices. > Oops, I missed that. Still, the form of this is unusual so please change it to the more conventional option of a goto per error rather than grouping them. That will also allow you to drop the null checks below leading to a more obviously correct error path. > >>> 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; >>> } >>> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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