[PATCH bpf v2] libbpf: fix to reject unknown flags in xsk_socket__create()

[Magnus Karlsson]

In xsk_socket__create(), the libbpf_flags field was not checked for
setting currently unused/unknown flags. This patch fixes that by returning
-EINVAL if the user has set any flag that is not in use at this point
in time.

Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
Reviewed-by: Andrii Nakryiko <andrii.nakry...@gmail.com>
Signed-off-by: Magnus Karlsson <magnus.karls...@intel.com>
---
 tools/lib/bpf/xsk.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index f98ac82..8d0078b 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -126,8 +126,8 @@ static void xsk_set_umem_config(struct xsk_umem_config *cfg,
        cfg->frame_headroom = usr_cfg->frame_headroom;
 }
 
-static void xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
-                                     const struct xsk_socket_config *usr_cfg)
+static int xsk_set_xdp_socket_config(struct xsk_socket_config *cfg,
+                                    const struct xsk_socket_config *usr_cfg)
 {
        if (!usr_cfg) {
                cfg->rx_size = XSK_RING_CONS__DEFAULT_NUM_DESCS;
@@ -135,14 +135,19 @@ static void xsk_set_xdp_socket_config(struct 
xsk_socket_config *cfg,
                cfg->libbpf_flags = 0;
                cfg->xdp_flags = 0;
                cfg->bind_flags = 0;
-               return;
+               return 0;
        }
 
+       if (usr_cfg->libbpf_flags & ~XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)
+               return -EINVAL;
+
        cfg->rx_size = usr_cfg->rx_size;
        cfg->tx_size = usr_cfg->tx_size;
        cfg->libbpf_flags = usr_cfg->libbpf_flags;
        cfg->xdp_flags = usr_cfg->xdp_flags;
        cfg->bind_flags = usr_cfg->bind_flags;
+
+       return 0;
 }
 
 int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
@@ -557,7 +562,9 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const 
char *ifname,
        }
        strncpy(xsk->ifname, ifname, IFNAMSIZ);
 
-       xsk_set_xdp_socket_config(&xsk->config, usr_config);
+       err = xsk_set_xdp_socket_config(&xsk->config, usr_config);
+       if (err)
+               goto out_socket;
 
        if (rx) {
                err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING,
-- 
2.7.4