On Mon, Mar 18, 2024 at 11:02:12PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> We expect nc->if_name to be NUL-terminated based on existing manual
> NUL-byte assignments and checks:
> | nc.if_name[IFNAMSIZ-1] = '\0';
> ...
> | if (nc->if_name[0] != '\0')
>
> Let's use the new 2-argument strscpy() since it guarantees
> NUL-termination on the destination buffer while correctly using the
> destination buffers size to bound the operation.
We may need for -rc1 (or -rc2), depending on when subsystem tree re-open
for landing patches to use the 2-arg versio, but, regardless, it looks
right:
Reviewed-by: Kees Cook <[email protected]>
-Kees
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
> drivers/tty/n_gsm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 4036566febcb..f5b0d91d32a7 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -4010,7 +4010,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
> mux_net = netdev_priv(net);
> mux_net->dlci = dlci;
> kref_init(&mux_net->ref);
> - strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */
> + strscpy(nc->if_name, net->name); /* return net name */
>
> /* reconfigure dlci for network */
> dlci->prev_adaption = dlci->adaption;
>
> ---
> base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
> change-id: 20240318-strncpy-drivers-tty-n_gsm-c-ab1336e0e196
>
> Best regards,
> --
> Justin Stitt <[email protected]>
>
>
--
Kees Cook