From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout3.w1.samsung.com ([210.118.77.13]:24186 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751258AbaCQIBR (ORCPT ); Mon, 17 Mar 2014 04:01:17 -0400 Message-id: <1395043273.3950.3.camel@AMDC1943> Subject: Re: [PATCH] iio: cm36651: Fix i2c client leak and possible NULL pointer dereference From: Krzysztof Kozlowski To: Jonathan Cameron Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Beomho Seo , Lars-Peter Clausen Date: Mon, 17 Mar 2014 09:01:13 +0100 In-reply-to: <53247EC9.6090505@kernel.org> References: <1394098390-11213-1-git-send-email-k.kozlowski@samsung.com> <53247EC9.6090505@kernel.org> Content-type: text/plain; charset=UTF-8 MIME-version: 1.0 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org 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 > 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. > > 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; > > } > >