On Mon, Jul 1, 2019 at 10:47 PM Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> GCC8 started emitting warning about using strncpy with number of bytes
> exactly equal destination size, which is generally unsafe, as can lead
> to non-zero terminated string being copied. Use IFNAMSIZ - 1 as number
> of bytes to ensure name is always zero-terminated.
>
> Cc: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> ---
> tools/lib/bpf/xsk.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index bf15a80a37c2..9588e7f87d0b 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -327,7 +327,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
>
> channels.cmd = ETHTOOL_GCHANNELS;
> ifr.ifr_data = (void *)&channels;
> - strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ);
> + strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
To accommodate the xsk->ifname string length FNAMSIZ - 1, we need to have
ifr.ifr_name[FNAMSIZ - 1] = '\0';
right?
> err = ioctl(fd, SIOCETHTOOL, &ifr);
> if (err && errno != EOPNOTSUPP) {
> ret = -errno;
> --
> 2.17.1
>
