libbpf: silence GCC8 warning about string truncation

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.

v1->v2:
- rebase against bpf tree.

Cc: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index e02025bbe36ddb69621461e4e0cfaa8ed1f66a14..680e63066cf39c7f3bd06cdf645b05065060728e 100644 (file)
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -326,7 +326,7 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
                return -errno;
 
        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) {
@@ -516,7 +516,7 @@ 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);