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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id v5-20020a63bf05000000b00563826c66eesm1564290pgf.61.2023.09.14.20.18.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Sep 2023 20:18:44 -0700 (PDT) Date: Thu, 14 Sep 2023 20:18:44 -0700 From: Kees Cook To: Justin Stitt Cc: Willy Tarreau , Ksenija Stanojevic , Miguel Ojeda , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] auxdisplay: panel: refactor deprecated strncpy Message-ID: <202309142018.CAD22C6D@keescook> References: <20230911-strncpy-drivers-auxdisplay-panel-c-v1-1-b60bd0ae8552@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230911-strncpy-drivers-auxdisplay-panel-c-v1-1-b60bd0ae8552@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 -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-hardening@vger.kernel.org > Cc: Kees Cook > Signed-off-by: Justin Stitt > --- > 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 > -- Kees Cook