linux-kernel - Re: [PATCH v2] thermal/int340x_thermal: Check for null pointer after calling kmemdup

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Message-ID: <CAJZ5v0hmb_4zC8FtMff1=v7uRF8DeH7sD7+UtBtD7JJXOrOCew@mail.gmail.com>
Date:   Tue, 25 Jan 2022 18:39:12 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Zhang, Rui" <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] thermal/int340x_thermal: Check for null pointer after
 calling kmemdup

On Fri, Jan 7, 2022 at 3:44 PM Jiasheng Jiang <jiasheng@...as.ac.cn> wrote:
>
> As the possible failure of the allocation, kmemdup() may return NULL
> pointer.
> Then the 'bin_attr_data_vault.private' will be NULL pointer but the
> 'bin_attr_data_vault.size' is not 0.
> Therefore, it should be better to check the return value of kmemdup() to
> avoid the wrong size.
>
> Fixes: 0ba13c763aac ("thermal/int340x_thermal: Export GDDV")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog
>
> v1 -> v2
>
> * Change 1. Use out_kfree to simplify the code.
> ---
>  .../thermal/intel/int340x_thermal/int3400_thermal.c  | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> index 19926beeb3b7..f869aeb087d3 100644
> --- a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> +++ b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> @@ -457,17 +457,21 @@ static void int3400_setup_gddv(struct int3400_thermal_priv *priv)
>
>         obj = buffer.pointer;
>         if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 1
> -           || obj->package.elements[0].type != ACPI_TYPE_BUFFER) {
> -               kfree(buffer.pointer);
> -               return;
> -       }
> +           || obj->package.elements[0].type != ACPI_TYPE_BUFFER)
> +               goto out_kfree;

This change isn't strictly necessary.

>
>         priv->data_vault = kmemdup(obj->package.elements[0].buffer.pointer,
>                                    obj->package.elements[0].buffer.length,
>                                    GFP_KERNEL);
> +       if (!priv->data_vault)
> +               goto out_kfree;
> +
>         bin_attr_data_vault.private = priv->data_vault;
>         bin_attr_data_vault.size = obj->package.elements[0].buffer.length;
>         kfree(buffer.pointer);
> +
> +out_kfree:
> +       kfree(buffer.pointer);

On success, this would be the second kfree() for the same pointer in a
row, which would be a bug.

>  }
>
>  static int int3400_thermal_probe(struct platform_device *pdev)
> --