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

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Message-ID: <OS0PR01MB5922F2C8D5B17A614215ED7B86EC9@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Wed, 13 Apr 2022 08:47:56 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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>,
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        <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

Hi Krzysztof Kozlowski,

> 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,
> > rpdev->"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.
> 

OK, it's a suggestion as same string constant duplicated thrice,

Any change in this string constant in future will need changes
in 3 places , by using "rpdev->id.name", the change is limited
to 1 place.

Cheers,
Biju