[PATCH bpf] libbpf: fix another GCC8 warning for strncpy

[Andrii Nakryiko]

Similar issue was fixed in cdfc7f888c2a ("libbpf: fix GCC8 warning for
strncpy") already. This one was missed. Fixing now.

Cc: Magnus Karlsson <magnus.karls...@intel.com>
Signed-off-by: Andrii Nakryiko <andr...@fb.com>
---
 tools/lib/bpf/xsk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index b33740221b7e..5007b5d4fd2c 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -517,7 +517,8 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const 
char *ifname,
                err = -errno;
                goto out_socket;
        }
-       strncpy(xsk->ifname, ifname, IFNAMSIZ);
+       strncpy(xsk->ifname, ifname, IFNAMSIZ - 1);
+       xsk->ifname[IFNAMSIZ - 1] = '\0';
 
        err = xsk_set_xdp_socket_config(&xsk->config, usr_config);
        if (err)
-- 
2.17.1