linux-kernel - Re: [RFC 0/4] clk/driver: platform: Fix kfree() of const memory on setting driver

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Message-ID: <CAMuHMdWXy_0zL8FZWapPj4+cXRd0wHy9buLhf0D0txpAHPkK7Q@mail.gmail.com>
Date:   Mon, 18 Feb 2019 11:40:12 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Kukjin Kim <kgene@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-samsung-soc@...r.kernel.org,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm@...r.kernel.org,
        ALSA Development Mailing List <alsa-devel@...a-project.org>
Subject: Re: [RFC 0/4] clk/driver: platform: Fix kfree() of const memory on
 setting driver_override

Hi Krzysztof,

On Mon, Feb 18, 2019 at 11:27 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
> The problem
> ===========
> Several device types (platform, amba, spi etc.) provide a driver_override
> field.  On sysfs store or during device removal, they kfree() the
> existing value.
>
> However the users are unaware of this and set the driver_override like:
>
>         pdev->driver_override = "exynos5-subcmu";
>
> which obviously leads to error.

IMHO driver_override is not meant to be set by a driver, only from userspace,
for binding the device to vfio (is there another use case?).

>   clk: samsung: exynos5: Fix kfree() of const memory on setting
>     driver_override
>   slimbus: ngd: Fix kfree() of const memory on setting driver_override

I see all users set override immediately after allocating a platform device.
Can't they just allocate a platform device using the override name instead?
What am I missing?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds