From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-id: <1395130095.13308.0.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: Tue, 18 Mar 2014 09:08:15 +0100 In-reply-to: <53274BDA.9070804@kernel.org> References: <1394098390-11213-1-git-send-email-k.kozlowski@samsung.com> <53247EC9.6090505@kernel.org> <1395043273.3950.3.camel@AMDC1943> <53274BDA.9070804@kernel.org> Content-type: text/plain; charset=UTF-8 MIME-version: 1.0 List-ID: On Mon, 2014-03-17 at 19:24 +0000, Jonathan Cameron wrote: > 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 > >> 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. Sure, I'll send a fixed version. Best regards, Krzysztof