linux-kernel - Re: [PATCH] thermal: mtk: Allocate enough space for mtk

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Date:   Wed, 30 Jan 2019 17:25:27 +0800
From:   Pi-Hsun Shih <pihsun@...omium.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Michael.Kao@...iatek.com
Subject: Re: [PATCH] thermal: mtk: Allocate enough space for mtk_thermal.

On Wed, Jan 30, 2019 at 3:44 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> On 30/01/2019 07:04, Peter Shih wrote:
> > Adding Michael Kao to cc list.
> >
> > On Wed, Jan 9, 2019 at 1:57 PM Pi-Hsun Shih <pihsun@...omium.org> wrote:
> >>
> >> The mtk_thermal struct contains a 'struct mtk_thermal_bank banks[];',
> >> but the allocation only allocates sizeof(struct mtk_thermal) bytes,
> >> which cause out of bound access with the ->banks[] member. Change it to
> >> a fixed size array instead.
>
> Even if the fix is correct, it pushes back the bug later in time if a
> new board containing more than MAX_NUM_ZONES is introduced. I suggest to
> dynamically allocate the array with the 'num_banks' value.
>

For the current code structure, those mtk_thermal_data are statically declared,
so if there's new board containing more than MAX_NUM_ZONES of bank_data, it
would actually be a compile error.

I'm fine with either way, but feel like that this is simpler than manually
calculating the size needed for allocation.

>
> >> Signed-off-by: Pi-Hsun Shih <pihsun@...omium.org>
> >> ---
> >>  drivers/thermal/mtk_thermal.c | 7 +++++--
> >>  1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/thermal/mtk_thermal.c b/drivers/thermal/mtk_thermal.c
> >> index 0691f260f6eabe..ea11edb3fcced6 100644
> >> --- a/drivers/thermal/mtk_thermal.c
> >> +++ b/drivers/thermal/mtk_thermal.c
> >> @@ -159,6 +159,9 @@
> >>  #define MT7622_NUM_SENSORS_PER_ZONE    1
> >>  #define MT7622_TS1     0
> >>
> >> +/* The maximum number of banks */
> >> +#define MAX_NUM_ZONES          8
> >> +
> >>  struct mtk_thermal;
> >>
> >>  struct thermal_bank_cfg {
> >> @@ -178,7 +181,7 @@ struct mtk_thermal_data {
> >>         const int *sensor_mux_values;
> >>         const int *msr;
> >>         const int *adcpnp;
> >> -       struct thermal_bank_cfg bank_data[];
> >> +       struct thermal_bank_cfg bank_data[MAX_NUM_ZONES];
> >>  };
> >>
> >>  struct mtk_thermal {
> >> @@ -197,7 +200,7 @@ struct mtk_thermal {
> >>         s32 vts[MT8173_NUM_SENSORS];
> >>
> >>         const struct mtk_thermal_data *conf;
> >> -       struct mtk_thermal_bank banks[];
> >> +       struct mtk_thermal_bank banks[MAX_NUM_ZONES];
> >>  };
> >>
> >>  /* MT8173 thermal sensor data */
> >> --
> >> 2.20.1.97.g81188d93c3-goog
> >>
>
>
> --
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