bpf, libbpf: fix segfault in bpf_object__init_maps' pr_debug statement

Ran into it while testing; in bpf_object__init_maps() data can be NULL
in the case where no map section is present. Therefore we simply cannot
access data->d_size before NULL test. Move the pr_debug() where it's
safe to access.

Fixes: d859900c4c56 ("bpf, libbpf: support global data/bss/rodata sections")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 85315de..9052061 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -875,14 +875,14 @@ bpf_object__init_maps(struct bpf_object *obj, int flags)
                nr_maps++;
        }
 
-       /* Alloc obj->maps and fill nr_maps. */
-       pr_debug("maps in %s: %d maps in %zd bytes\n", obj->path,
-                nr_maps, data->d_size);
        if (!nr_maps && !nr_maps_glob)
                return 0;
 
        /* Assume equally sized map definitions */
        if (data) {
+               pr_debug("maps in %s: %d maps in %zd bytes\n", obj->path,
+                        nr_maps, data->d_size);
+
                map_def_sz = data->d_size / nr_maps;
                if (!data->d_size || (data->d_size % nr_maps) != 0) {
                        pr_warning("unable to determine map definition size "