linux-kernel - Re: [PATCH] clk: samsung: Suppress unbinding to prevent theoretical attacks

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Message-ID: <CA+Ln22E13nm4nsgWoi6gNc_Jh+UqqE5MgwANH02GZF7bQye+yw@mail.gmail.com>
Date:	Sat, 18 Jun 2016 23:37:31 +0900
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Kukjin Kim <kgene@...nel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, linux-clk@...r.kernel.org,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH] clk: samsung: Suppress unbinding to prevent theoretical attacks

Hi,

2016-05-17 16:26 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@...sung.com>:
> Although unbinding a driver requires root privileges but it still might
> be used theoretically in certain attacks (by triggering NULL pointer
> exception or memory corruption if driver does not provide proper remove
> callbacks or core does not handle it).
>
> Samsung clock drivers are essential for system operation so their
> removal is not expected. More over, the Exynos3250 ISP clock driver does
> not implement remove() driver callback and it is not buildable as
> modules.
>
> Suppress the unbind interface for Exynos3250 ISP and S3C2410 DCLK clock
> drivers.
>
> Suggested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> ---
>  drivers/clk/samsung/clk-exynos3250.c   | 1 +
>  drivers/clk/samsung/clk-s3c2410-dclk.c | 5 +++--
>  2 files changed, 4 insertions(+), 2 deletions(-)

Makes sense. (By the way, I wonder if we ever see a solution for the
unbind problem with .remove implemented and some resources that can't
be released at the time .unbind is attempted...)

Acked-by: Tomasz Figa <tomasz.figa@...il.com>

Best regards,
Tomasz