linux-kernel - Re: [PATCH] clk: divider: fix incorrect usage of container

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Message-ID: <20171221183836.GL7997@codeaurora.org>
Date:   Thu, 21 Dec 2017 10:38:36 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Clark <robdclark@...il.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.or,
        linux-rtc@...r.kernel.org
Subject: Re: [PATCH] clk: divider: fix incorrect usage of container_of

On 12/21, Jerome Brunet wrote:
> divider_recalc_rate() is an helper function used by clock divider of
> different types, so the structure containing the 'hw' pointer is not
> always a 'struct clk_divider'
> 
> At the following line:
> > div = _get_div(table, val, flags, divider->width);
> 
> in several cases, the value of 'divider->width' is garbage as the actual
> structure behind this memory is not a 'struct clk_divider'
> 
> Fortunately, this width value is used by _get_val() only when
> CLK_DIVIDER_MAX_AT_ZERO flag is set. This has never been the case so
> far when the structure is not a 'struct clk_divider'. This is probably
> why we did not notice this bug before
> 
> Fixes: afe76c8fd030 ("clk: allow a clk divider with max divisor when zero")
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
> Hi Stephen, Mike,
> 
> In addition to clock, this patch also touch the rtc and drm directories.
> As it is changing the API of the helper function, I have this fix in a
> single commit to avoid breaking bisect.
> 
> Please let me know if you prefer to do differently.
> 

Looks good. Thanks for catching this before it became a real
problem. It would be good to get acks from DRM and RTC
maintainers.

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