On Wed, Jul 24, 2019 at 4:33 AM Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> Despite a proper NULL-termination after strncpy(..., ..., IFNAMSIZ - 1),
> GCC8 still complains about *expected* string truncation:
>
> xsk.c:330:2: error: 'strncpy' output may be truncated copying 15 bytes
> from a string of length 15 [-Werror=stringop-truncation]
> strncpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
>
> This patch gets rid of the issue altogether by using memcpy instead.
> There is no performance regression, as strncpy will still copy and fill
> all of the bytes anyway.
Let us make GCC8 happy then :-). Thanks Andrii.
Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> Cc: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> ---
> tools/lib/bpf/xsk.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index 5007b5d4fd2c..65f5dd556f99 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 - 1);
> + memcpy(ifr.ifr_name, xsk->ifname, IFNAMSIZ - 1);
> ifr.ifr_name[IFNAMSIZ - 1] = '\0';
> err = ioctl(fd, SIOCETHTOOL, &ifr);
> if (err && errno != EOPNOTSUPP) {
> @@ -517,7 +517,7 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
> err = -errno;
> goto out_socket;
> }
> - strncpy(xsk->ifname, ifname, IFNAMSIZ - 1);
> + memcpy(xsk->ifname, ifname, IFNAMSIZ - 1);
> xsk->ifname[IFNAMSIZ - 1] = '\0';
>
> err = xsk_set_xdp_socket_config(&xsk->config, usr_config);
> --
> 2.17.1
>
