Date:   Tue, 16 Jun 2020 21:56:38 +0200 (CEST)
From:   Clément Leger <cleger@...ray.eu>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rpmsg: fix driver_override memory leak


----- On 16 Jun, 2020, at 21:13, Mathieu Poirier mathieu.poirier@...aro.org wrote:

> On Tue, 16 Jun 2020 at 11:19, Clément Leger <cleger@...ray.eu> wrote:
>>
>> Hi Mathieu,
>>
>> ----- On 16 Jun, 2020, at 19:10, Mathieu Poirier mathieu.poirier@...aro.org
>> wrote:
>>
>> > Hi Clément,
>> >
>> > On Thu, Jun 11, 2020 at 08:50:12PM +0200, Clement Leger wrote:
>> >> rpmsg_core allows to override driver using driver_override sysfs
>> >> attribute. When used, the sysfs store function will duplicate the user
>> >> provided string using kstrndup. However, when the rpdev is released,
>> >> the driver_override attribute is not freed. In order to have a
>> >> consistent allocation and release, use kstrdup in
>> >> rpmsg_chrdev_register_device and move it in rpmsg_core.c to avoid
>> >> header dependencies. Moreover, add a rpmsg_release_device function to
>> >> be called in device release. Drivers using rpmsg have been modified to
>> >> use this function and ensure there will be no more memory leak when
>> >> releasing rpmsg devices.
>> >> This was found with kmemleak while using remoteproc and virtio.
>> >>
>> >> Signed-off-by: Clement Leger <cleger@...ray.eu>
>> >> ---
>> >>  drivers/rpmsg/qcom_glink_native.c |  1 +
>> >>  drivers/rpmsg/qcom_smd.c          |  1 +
>> >>  drivers/rpmsg/rpmsg_core.c        | 22 ++++++++++++++++++++++
>> >>  drivers/rpmsg/rpmsg_internal.h    | 15 ++-------------
>> >>  drivers/rpmsg/virtio_rpmsg_bus.c  |  1 +
>> >>  5 files changed, 27 insertions(+), 13 deletions(-)
>> >>
>> >> diff --git a/drivers/rpmsg/qcom_glink_native.c
>> >> b/drivers/rpmsg/qcom_glink_native.c
>> >> index 1995f5b3ea67..076997afc638 100644
>> >> --- a/drivers/rpmsg/qcom_glink_native.c
>> >> +++ b/drivers/rpmsg/qcom_glink_native.c
>> >> @@ -1373,6 +1373,7 @@ static void qcom_glink_rpdev_release(struct device *dev)
>> >>      struct glink_channel *channel = to_glink_channel(rpdev->ept);
>> >>
>> >>      channel->rpdev = NULL;
>> >> +    rpmsg_release_device(rpdev);
>> >>      kfree(rpdev);
>> >>  }
>> >>
>> >> diff --git a/drivers/rpmsg/qcom_smd.c b/drivers/rpmsg/qcom_smd.c
>> >> index 4abbeea782fa..f01174d0d4d9 100644
>> >> --- a/drivers/rpmsg/qcom_smd.c
>> >> +++ b/drivers/rpmsg/qcom_smd.c
>> >> @@ -1047,6 +1047,7 @@ static void qcom_smd_release_device(struct device *dev)
>> >>      struct rpmsg_device *rpdev = to_rpmsg_device(dev);
>> >>      struct qcom_smd_device *qsdev = to_smd_device(rpdev);
>> >>
>> >> +    rpmsg_release_device(rpdev);
>> >>      kfree(qsdev);
>> >>  }
>> >>
>> >> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
>> >> index a6361cad608b..31de89c81b27 100644
>> >> --- a/drivers/rpmsg/rpmsg_core.c
>> >> +++ b/drivers/rpmsg/rpmsg_core.c
>> >> @@ -554,6 +554,28 @@ int rpmsg_unregister_device(struct device *parent,
>> >>  }
>> >>  EXPORT_SYMBOL(rpmsg_unregister_device);
>> >>
>> >> +void rpmsg_release_device(struct rpmsg_device *rpdev)
>> >> +{
>> >> +    kfree(rpdev->driver_override);
>> >> +}
>> >> +EXPORT_SYMBOL(rpmsg_release_device);
>> >> +
>> >> +/**
>> >> + * rpmsg_chrdev_register_device() - register chrdev device based on rpdev
>> >> + * @rpdev:  prepared rpdev to be used for creating endpoints
>> >> + *
>> >> + * This function wraps rpmsg_register_device() preparing the rpdev for use as
>> >> + * basis for the rpmsg chrdev.
>> >> + */
>> >> +int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
>> >> +{
>> >> +    strcpy(rpdev->id.name, "rpmsg_chrdev");
>> >> +    rpdev->driver_override = kstrdup("rpmsg_chrdev", GFP_KERNEL);
>> >
>> > Have you considered using devm_kstrdup() instead?  Since the same rpdev is
>> > available here and in field##_store(), proceeding that way would prevent the
>> > need to add a new rpmsg_release_device() function.  Depending on header
>> > dependencies rpmsg_chrdev_register_device() may also be able to remain in
>> > rpmsg_internal.h.
>>
>> Indeed, using devm_kstrdup would be better. Regarding the use of kstrdup in
>> headers, I only found a really really few occurences of such usage in the
>> whole kernel. If you think it's ok, I can go go with it though.
> 
> I don't see an issue with using devm_kstrdup() in a header file.

Ok, anyway after looking more thoroughly in using devm_kstrndup, it will
be possible to make the modification really localized in sysfs store only.
I just have to add devm_kstrndup which does not exists yet.

> 
>>
>> Thanks,
>>
>> Clément
>>
>> >
>> > Thanks,
>> > Mathieu
>> >
>> >> +
>> >> +    return rpmsg_register_device(rpdev);
>> >> +}
>> >> +EXPORT_SYMBOL(rpmsg_chrdev_register_device);
>> >> +
>> >>  /**
>> >>   * __register_rpmsg_driver() - register an rpmsg driver with the rpmsg bus
>> >>   * @rpdrv: pointer to a struct rpmsg_driver
>> >> diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
>> >> index 3fc83cd50e98..043b28f912fd 100644
>> >> --- a/drivers/rpmsg/rpmsg_internal.h
>> >> +++ b/drivers/rpmsg/rpmsg_internal.h
>> >> @@ -75,19 +75,8 @@ int rpmsg_unregister_device(struct device *parent,
>> >>  struct device *rpmsg_find_device(struct device *parent,
>> >>                               struct rpmsg_channel_info *chinfo);
>> >>
>> >> -/**
>> >> - * rpmsg_chrdev_register_device() - register chrdev device based on rpdev
>> >> - * @rpdev:  prepared rpdev to be used for creating endpoints
>> >> - *
>> >> - * This function wraps rpmsg_register_device() preparing the rpdev for use as
>> >> - * basis for the rpmsg chrdev.
>> >> - */
>> >> -static inline int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev)
>> >> -{
>> >> -    strcpy(rpdev->id.name, "rpmsg_chrdev");
>> >> -    rpdev->driver_override = "rpmsg_chrdev";
>> >> +int rpmsg_chrdev_register_device(struct rpmsg_device *rpdev);
>> >>
>> >> -    return rpmsg_register_device(rpdev);
>> >> -}
>> >> +void rpmsg_release_device(struct rpmsg_device *rpdev);
>> >>
>> >>  #endif
>> >> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
>> >> index 07d4f3374098..af4ea6170f89 100644
>> >> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
>> >> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
>> >> @@ -381,6 +381,7 @@ static void virtio_rpmsg_release_device(struct device *dev)
>> >>      struct rpmsg_device *rpdev = to_rpmsg_device(dev);
>> >>      struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
>> >>
>> >> +    rpmsg_release_device(rpdev);
>> >>      kfree(vch);
>> >>  }
>> >>
>> >> --
> > >> 2.17.1

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