linux-kernel - Re: [PATCH] ACPI: video: Fix a null-pointer-dereference in acpi_video_bus

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Date:   Mon, 25 Sep 2023 11:54:57 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Michal Wilczynski <michal.wilczynski@...el.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: video: Fix a null-pointer-dereference in acpi_video_bus_add

On Mon, Sep 25, 2023 at 10:09 AM Dinghao Liu <dinghao.liu@....edu.cn> wrote:
>
> acpi_video_bus_add_notify_handler() could free video->input and
> set it to NULL on failure, but this failure will be missed in its
> caller acpi_video_bus_add(). As a result, when an error happens in
> acpi_dev_install_notify_handler(), acpi_video_bus_add() will call
> acpi_video_bus_remove_notify_handler(), where a potential null pointer
> video->input is dereferenced in input_unregister_device().
>
> Fix this by adding a return value check and adjusting the following
> error handling code.
>
> Fixes: 6f7016819766 ("ACPI: video: Install Notify() handler directly")
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/acpi/acpi_video.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
> index 948e31f7ce6e..b411948594ff 100644
> --- a/drivers/acpi/acpi_video.c
> +++ b/drivers/acpi/acpi_video.c
> @@ -2057,7 +2057,9 @@ static int acpi_video_bus_add(struct acpi_device *device)
>             !auto_detect)
>                 acpi_video_bus_register_backlight(video);
>
> -       acpi_video_bus_add_notify_handler(video);
> +       error = acpi_video_bus_add_notify_handler(video);
> +       if (error)
> +               goto err_del;
>
>         error = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
>                                                 acpi_video_bus_notify);
> @@ -2067,10 +2069,11 @@ static int acpi_video_bus_add(struct acpi_device *device)
>         return 0;
>
>  err_remove:
> +       acpi_video_bus_remove_notify_handler(video);
> +err_del:
>         mutex_lock(&video_list_lock);
>         list_del(&video->entry);
>         mutex_unlock(&video_list_lock);
> -       acpi_video_bus_remove_notify_handler(video);
>         acpi_video_bus_unregister_backlight(video);
>  err_put_video:
>         acpi_video_bus_put_devices(video);
> --

Applied as 6.6-rc material, thanks!