On Mon, Sep 11, 2023 at 08:51:04PM +0000, Justin Stitt wrote:
> `strncpy` is deprecated and as such we should prefer more robust and
> less ambiguous interfaces.
>
> In this case, all of `press_str`, `repeat_str` and `release_str` are
> explicitly marked as nonstring:
> | struct { /* valid when type == INPUT_TYPE_KBD */
> | char press_str[sizeof(void *) + sizeof(int)] __nonstring;
> | char repeat_str[sizeof(void *) + sizeof(int)] __nonstring;
> | char release_str[sizeof(void *) + sizeof(int)] __nonstring;
> | } kbd;
>
> ... which makes `strtomem_pad` a suitable replacement as it is
> functionally the same whilst being more obvious about its behavior.
Yup, this is exactly what strtomem_pad() was made for. :)
Reviewed-by: Kees Cook <keesc...@chromium.org>
-Kees
>
> Link:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
> [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-harden...@vger.kernel.org
> Cc: Kees Cook <keesc...@chromium.org>
> Signed-off-by: Justin Stitt <justinst...@google.com>
> ---
> Note: build-tested
> ---
> drivers/auxdisplay/panel.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c
> index eba04c0de7eb..e20d35bdf5fe 100644
> --- a/drivers/auxdisplay/panel.c
> +++ b/drivers/auxdisplay/panel.c
> @@ -1449,10 +1449,9 @@ static struct logical_input *panel_bind_key(const char
> *name, const char *press,
> key->rise_time = 1;
> key->fall_time = 1;
>
> - strncpy(key->u.kbd.press_str, press, sizeof(key->u.kbd.press_str));
> - strncpy(key->u.kbd.repeat_str, repeat, sizeof(key->u.kbd.repeat_str));
> - strncpy(key->u.kbd.release_str, release,
> - sizeof(key->u.kbd.release_str));
> + strtomem_pad(key->u.kbd.press_str, press, '\0');
> + strtomem_pad(key->u.kbd.repeat_str, repeat, '\0');
> + strtomem_pad(key->u.kbd.release_str, release, '\0');
> list_add(&key->list, &logical_inputs);
> return key;
> }
>
> ---
> base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
> change-id: 20230911-strncpy-drivers-auxdisplay-panel-c-83bce51f32cb
>
> Best regards,
> --
> Justin Stitt <justinst...@google.com>
>
--
Kees Cook
