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From:   ChiYuan Huang <u0084500@gmail.com>
Date:   Thu, 20 Oct 2022 15:46:17 +0800
Message-ID: <CADiBU38+r48uxAasbHSCEFvJc2w4_-nz8vHpAX=OOBq2NPE81Q@mail.gmail.com>
Subject: Re: [PATCH v2] mfd: mt6360: add bound check in regmap read/write function
To:     lee@kernel.org
Cc:     matthias.bgg@gmail.com, gene_chen@richtek.com,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        ChiYuan Huang <cy_huang@richtek.com>, stable@vger.kernel.org
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Hi,

cy_huang <u0084500@gmail.com> =E6=96=BC 2022=E5=B9=B49=E6=9C=8829=E6=97=A5 =
=E9=80=B1=E5=9B=9B =E4=B8=8A=E5=8D=8810:00=E5=AF=AB=E9=81=93=EF=BC=9A
>
> From: ChiYuan Huang <cy_huang@richtek.com>
>
> Fix the potential risk for null pointer if bank index is over the maximum=
.
>
> Refer to the discussion list for the experiment result on mt6370.
> https://lore.kernel.org/all/20220914013345.GA5802@cyhuang-hp-elitebook-84=
0-g3.rt/
> If not to check the bound, there is the same issue on mt6360.
>
> Fixes: 3b0850440a06c (mfd: mt6360: Merge different sub-devices I2C read/w=
rite)
> Cc: stable@vger.kernel.org
> Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
> ---
> Since v2:
> - Assign i2c bank variable after bank index is already checked.
>
> ---
>  drivers/mfd/mt6360-core.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
Any comment?
> diff --git a/drivers/mfd/mt6360-core.c b/drivers/mfd/mt6360-core.c
> index 6eaa677..d3b32eb 100644
> --- a/drivers/mfd/mt6360-core.c
> +++ b/drivers/mfd/mt6360-core.c
> @@ -402,7 +402,7 @@ static int mt6360_regmap_read(void *context, const vo=
id *reg, size_t reg_size,
>         struct mt6360_ddata *ddata =3D context;
>         u8 bank =3D *(u8 *)reg;
>         u8 reg_addr =3D *(u8 *)(reg + 1);
> -       struct i2c_client *i2c =3D ddata->i2c[bank];
> +       struct i2c_client *i2c;
>         bool crc_needed =3D false;
>         u8 *buf;
>         int buf_len =3D MT6360_ALLOC_READ_SIZE(val_size);
> @@ -410,6 +410,11 @@ static int mt6360_regmap_read(void *context, const v=
oid *reg, size_t reg_size,
>         u8 crc;
>         int ret;
>
> +       if (bank >=3D MT6360_SLAVE_MAX)
> +               return -EINVAL;
> +
> +       i2c =3D ddata->i2c[bank];
> +
>         if (bank =3D=3D MT6360_SLAVE_PMIC || bank =3D=3D MT6360_SLAVE_LDO=
) {
>                 crc_needed =3D true;
>                 ret =3D mt6360_xlate_pmicldo_addr(&reg_addr, val_size);
> @@ -453,13 +458,18 @@ static int mt6360_regmap_write(void *context, const=
 void *val, size_t val_size)
>         struct mt6360_ddata *ddata =3D context;
>         u8 bank =3D *(u8 *)val;
>         u8 reg_addr =3D *(u8 *)(val + 1);
> -       struct i2c_client *i2c =3D ddata->i2c[bank];
> +       struct i2c_client *i2c;
>         bool crc_needed =3D false;
>         u8 *buf;
>         int buf_len =3D MT6360_ALLOC_WRITE_SIZE(val_size);
>         int write_size =3D val_size - MT6360_REGMAP_REG_BYTE_SIZE;
>         int ret;
>
> +       if (bank >=3D MT6360_SLAVE_MAX)
> +               return -EINVAL;
> +
> +       i2c =3D ddata->i2c[bank];
> +
>         if (bank =3D=3D MT6360_SLAVE_PMIC || bank =3D=3D MT6360_SLAVE_LDO=
) {
>                 crc_needed =3D true;
>                 ret =3D mt6360_xlate_pmicldo_addr(&reg_addr, val_size - M=
T6360_REGMAP_REG_BYTE_SIZE);
> --
> 2.7.4
>