linux-kernel - Re: [PATCH v5 11/11] rpmsg: Fix kfree() of static memory on setting driver

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Message-ID: <0cc4e90d-c5e5-e6a3-6cc6-23d3058b9731@canonical.com>
Date:   Wed, 16 Mar 2022 20:38:09 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Stuart Yoder <stuyoder@...il.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andy Gross <agross@...nel.org>, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, NXP Linux Team <linux-imx@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-hyperv@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, linux-spi@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v5 11/11] rpmsg: Fix kfree() of static memory on setting
 driver_override

On 16/03/2022 16:08, Krzysztof Kozlowski wrote:
> The driver_override field from platform driver should not be initialized
> from static memory (string literal) because the core later kfree() it,
> for example when driver_override is set via sysfs.
> 
> Use dedicated helper to set driver_override properly.
> 
> Fixes: 950a7388f02b ("rpmsg: Turn name service into a stand alone driver")
> Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>  drivers/rpmsg/rpmsg_core.c     |  3 ++-
>  drivers/rpmsg/rpmsg_internal.h | 11 +++++++++--
>  drivers/rpmsg/rpmsg_ns.c       | 14 ++++++++++++--
>  include/linux/rpmsg.h          |  6 ++++--
>  4 files changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
> index 79368a957d89..95fc283f6af7 100644
> --- a/drivers/rpmsg/rpmsg_core.c
> +++ b/drivers/rpmsg/rpmsg_core.c
> @@ -400,7 +400,8 @@ field##_store(struct device *dev, struct device_attribute *attr,	\
>  	      const char *buf, size_t sz)				\
>  {									\
>  	struct rpmsg_device *rpdev = to_rpmsg_device(dev);		\
> -	char *new, *old;						\
> +	const char *old;						\
> +	char *new;							\
>  									\
>  	new = kstrndup(buf, sz, GFP_KERNEL);				\
>  	if (!new)							\
> diff --git a/drivers/rpmsg/rpmsg_internal.h b/drivers/rpmsg/rpmsg_internal.h
> index d4b23fd019a8..dd1f4ed616b6 100644
> --- a/drivers/rpmsg/rpmsg_internal.h
> +++ b/drivers/rpmsg/rpmsg_internal.h
> @@ -95,9 +95,16 @@ int rpmsg_release_channel(struct rpmsg_device *rpdev,
>  static inline int rpmsg_ctrldev_register_device(struct rpmsg_device *rpdev)
>  {
>  	strcpy(rpdev->id.name, "rpmsg_ctrl");
> -	rpdev->driver_override = "rpmsg_ctrl";
> +	ret = driver_set_override(&rpdev->dev, &rpdev->driver_override,
> +				  "rpmsg_ctrl", strlen("rpmsg_ctrl"));

I made here a mistake while rebasing. This will need a v6.

Best regards,
Krzysztof