Re: [PATCH] liquidio: replace deprecated strncpy with strscpy

Kees Cook
2023-10-05T23:22:32Z

On Thu, Oct 05, 2023 at 09:55:06PM +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.
>
> NUL-padding is not required as rep_cfg is memset to 0:
> | memset(&rep_cfg, 0, sizeof(rep_cfg));
>
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
>
> 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: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Note: build-tested only.
> ---
> drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c b/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> index 600de587d7a9..aa6c0dfb6f1c 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_vf_rep.c
> @@ -638,7 +638,8 @@ lio_vf_rep_netdev_event(struct notifier_block *nb,
> memset(&rep_cfg, 0, sizeof(rep_cfg));
> rep_cfg.req_type = LIO_VF_REP_REQ_DEVNAME;
> rep_cfg.ifidx = vf_rep->ifidx;
> - strncpy(rep_cfg.rep_name.name, ndev->name, LIO_IF_NAME_SIZE);
> + strscpy(rep_cfg.rep_name.name, ndev->name,
> + sizeof(rep_cfg.rep_name.name));

struct lio_vf_rep_req {
...
union {
struct lio_vf_rep_name {
char name[LIO_IF_NAME_SIZE];
} rep_name;

Yup, sizeof(rep_cfg.rep_name.name) == LIO_IF_NAME_SIZE.

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook