linux-kernel - Re: [PATCH v2 2/2] clk: samsung: exynos5: Fix kfree() of const memory on setting driver

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Message-ID: <155078479299.77512.7336673875297969172@swboyd.mtv.corp.google.com>
Date:   Thu, 21 Feb 2019 13:33:12 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Chanwoo Choi <cw00.choi@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] clk: samsung: exynos5: Fix kfree() of const memory on setting driver_override

Quoting Krzysztof Kozlowski (2019-02-21 03:45:52)
> Platform driver driver_override field should not be initialized from
> const memory because the core later kfree() it.  If driver_override is
> manually set later through sysfs, kfree() of old value leads to:
> 
>     $ echo "new_value" > /sys/bus/platform/drivers/.../driver_override
> 
>     kernel BUG at ../mm/slub.c:3960!
>     Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>     ...
>     (kfree) from [<c058e8c0>] (platform_set_driver_override+0x84/0xac)
>     (platform_set_driver_override) from [<c058e908>] (driver_override_store+0x20/0x34)
>     (driver_override_store) from [<c031f778>] (kernfs_fop_write+0x100/0x1dc)
>     (kernfs_fop_write) from [<c0296de8>] (__vfs_write+0x2c/0x17c)
>     (__vfs_write) from [<c02970c4>] (vfs_write+0xa4/0x188)
>     (vfs_write) from [<c02972e8>] (ksys_write+0x4c/0xac)
>     (ksys_write) from [<c0101000>] (ret_fast_syscall+0x0/0x28)
> 
> The clk-exynos5-subcmu driver uses override only for the purpose of
> creating meaningful names for children devices (matching names of power
> domains, e.g. DISP, MFC).  The driver_override was not developed for
> this purpose so just switch to default names of devices to fix the
> issue.
> 
> Fixes: b06a532bf1fa ("clk: samsung: Add Exynos5 sub-CMU clock driver")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> ---

Applied to clk-next