linux-kernel - Re: [PATCH v6 12/12] rpmsg: Fix kfree() of static memory on setting driver

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Date:   Wed, 13 Apr 2022 10:40:57 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Biju Das <biju.das.jz@...renesas.com>,
        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-kernel@...r.kernel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        NXP Linux Team <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v6 12/12] rpmsg: Fix kfree() of static memory on setting
 driver_override

On 12/04/2022 16:10, Biju Das wrote:
> Hi Krzysztof Kozlowski,
> 
> Thanks for the patch.
> 
>> Subject: [PATCH v6 12/12] rpmsg: Fix kfree() of static memory on setting
>> driver_override
>>
>> 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")
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
>> ---
>>  drivers/rpmsg/rpmsg_internal.h | 13 +++++++++++--
>>  drivers/rpmsg/rpmsg_ns.c       | 14 ++++++++++++--
>>  include/linux/rpmsg.h          |  6 ++++--
>>  3 files changed, 27 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/rpmsg/rpmsg_internal.h
>> b/drivers/rpmsg/rpmsg_internal.h index d4b23fd019a8..1a2fb8edf5d3 100644
>> --- a/drivers/rpmsg/rpmsg_internal.h
>> +++ b/drivers/rpmsg/rpmsg_internal.h
>> @@ -94,10 +94,19 @@ int rpmsg_release_channel(struct rpmsg_device *rpdev,
>>   */
>>  static inline int rpmsg_ctrldev_register_device(struct rpmsg_device
>> *rpdev)  {
>> +	int ret;
>> +
>>  	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"));
> 
> Is it not possible to use rpdev->id.name instead of "rpmsg_ctrl" ?
> rpdev->id.name has "rpmsg_ctrl" from strcpy(rpdev->id.name, "rpmsg_ctrl");
> 
> Same for "rpmsg_ns" as well

It's possible. I kept the pattern of duplicating the string literal
because original code had it, but I don't mind to change it. In the
output assembler that might be additional instruction - need to
dereference the rpdev pointer - but that does not matter much.


Best regards,
Krzysztof