libbpf: Deal with section with no data gracefully

ELF section data pointer returned by libelf may be NULL (if section has
SHT_NOBITS), so null check section data pointer before attempting to
copy license and kversion section.

Fixes: cb1e5e961991 ("bpf tools: Collect version and license from ELF sections")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221012022353.7350-3-shung-hsi.yu@suse.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2e8ac13..29e9df0 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1408,6 +1408,10 @@ static int bpf_object__check_endianness(struct bpf_object *obj)
 static int
 bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
 {
+       if (!data) {
+               pr_warn("invalid license section in %s\n", obj->path);
+               return -LIBBPF_ERRNO__FORMAT;
+       }
        /* libbpf_strlcpy() only copies first N - 1 bytes, so size + 1 won't
         * go over allowed ELF data section buffer
         */
@@ -1421,7 +1425,7 @@ bpf_object__init_kversion(struct bpf_object *obj, void *data, size_t size)
 {
        __u32 kver;
 
-       if (size != sizeof(kver)) {
+       if (!data || size != sizeof(kver)) {
                pr_warn("invalid kver section in %s\n", obj->path);
                return -LIBBPF_ERRNO__FORMAT;
        }