linux-kernel - Re: [PATCH 1/4] ACPI: battery: Fix missing NUL-termination with large strings

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Message-ID: <CAJZ5v0j6FMzHRhegQ-hQBmrrkHA=4rH6AeQOSmfTn5BcBW5dsw@mail.gmail.com>
Date:   Thu, 19 Jan 2023 14:34:25 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Armin Wolf <W_Armin@....de>
Cc:     rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] ACPI: battery: Fix missing NUL-termination with large strings

On Sat, Jan 14, 2023 at 9:51 AM Armin Wolf <W_Armin@....de> wrote:
>
> When encountering a string bigger than the destination buffer (32 bytes),
> the string is not properly NUL-terminated, causing buffer overreads later.
>
> This for example happens on the Inspiron 3505, where the battery
> model name is larger than 32 bytes, which leads to sysfs showing
> the model name together with the serial number string (which is
> NUL-terminated and thus prevents worse).
>
> Fix this by using strscpy() which ensures that the result is
> always NUL-terminated.
>
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
>  drivers/acpi/battery.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index f4badcdde76e..fb64bd217d82 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -440,7 +440,7 @@ static int extract_package(struct acpi_battery *battery,
>
>                         if (element->type == ACPI_TYPE_STRING ||
>                             element->type == ACPI_TYPE_BUFFER)
> -                               strncpy(ptr, element->string.pointer, 32);
> +                               strscpy(ptr, element->string.pointer, 32);
>                         else if (element->type == ACPI_TYPE_INTEGER) {
>                                 strncpy(ptr, (u8 *)&element->integer.value,
>                                         sizeof(u64));
> --

Applied as 6.3 material, thanks!

Please do not include this one in the next version of the series.