linux-kernel - Re: [PATCH] [ACPI] sbshc: Add error handling for acpi_driver

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Date:   Wed, 6 Dec 2023 21:10:46 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Haoran Liu <liuhaoran14@....com>
Cc:     rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [ACPI] sbshc: Add error handling for acpi_driver_data

On Wed, Nov 29, 2023 at 9:43 AM Haoran Liu <liuhaoran14@....com> wrote:
>
> This patch enhances the acpi_smbus_hc_add and acpi_smbus_hc_remove
> functions in drivers/acpi/sbshc.c by adding error handling for the
> acpi_driver_data calls. Previously, these functions did not check
> the return value of acpi_driver_data, potentially leading to
> stability issues if the function failed and returned a null pointer.

This needs to describe a real scenario in which acpi_driver_data() can
return NULL for each of the 2 places modified by the patch.

> Signed-off-by: Haoran Liu <liuhaoran14@....com>
> ---
>  drivers/acpi/sbshc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/acpi/sbshc.c b/drivers/acpi/sbshc.c
> index 16f2daaa2c45..1394104d3894 100644
> --- a/drivers/acpi/sbshc.c
> +++ b/drivers/acpi/sbshc.c
> @@ -267,6 +267,12 @@ static int acpi_smbus_hc_add(struct acpi_device *device)
>         init_waitqueue_head(&hc->wait);
>
>         hc->ec = acpi_driver_data(acpi_dev_parent(device));
> +       if (!hc->ec) {
> +               pr_err("Failed to retrieve parent ACPI device data\n");
> +               kfree(hc);
> +               return -ENODEV;
> +       }
> +
>         hc->offset = (val >> 8) & 0xff;
>         hc->query_bit = val & 0xff;
>         device->driver_data = hc;
> @@ -288,6 +294,11 @@ static void acpi_smbus_hc_remove(struct acpi_device *device)
>                 return;
>
>         hc = acpi_driver_data(device);
> +       if (!hc) {
> +               pr_err("Failed to retrieve ACPI SMBus HC data\n");
> +               return;
> +       }
> +
>         acpi_ec_remove_query_handler(hc->ec, hc->query_bit);
>         acpi_os_wait_events_complete();
>         kfree(hc);
> --
> 2.17.1
>