libbpf: Fix memory leak/double free issue

Coverity scan against Github libbpf code found the issue of not freeing memory and
leaving already freed memory still referenced from bpf_program. Fix it by
re-assigning successfully reallocated memory sooner.

Fixes: 2993e0515bb4 ("tools/bpf: add support to read .BTF.ext sections")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191107020855.3834758-2-andriin@fb.com

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index be4af95..3ef73a2 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3523,6 +3523,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
                        pr_warn("oom in prog realloc\n");
                        return -ENOMEM;
                }
+               prog->insns = new_insn;
 
                if (obj->btf_ext) {
                        err = bpf_program_reloc_btf_ext(prog, obj,
@@ -3534,7 +3535,6 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
 
                memcpy(new_insn + prog->insns_cnt, text->insns,
                       text->insns_cnt * sizeof(*insn));
-               prog->insns = new_insn;
                prog->main_prog_cnt = prog->insns_cnt;
                prog->insns_cnt = new_cnt;
                pr_debug("added %zd insn from %s to prog %s\n",