libbpf: Fix realloc usage in bpf_core_find_cands

commit 35b9211c0a2427e8f39e534f442f43804fc8d5ca upstream.

Fix bug requesting invalid size of reallocated array when constructing CO-RE
relocation candidate list. This can cause problems if there are many potential
candidates and a very fine-grained memory allocator bucket sizes are used.

Fixes: ddc7c3042614 ("libbpf: implement BPF CO-RE offset relocation algorithm")
Reported-by: William Smith <williampsmith@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200124201847.212528-1-andriin@fb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d98838c5820ce4a0752852df35ad490e0c4f057e..b6403712c2f4c43368877301f1541d9f3e23af4f 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2541,7 +2541,9 @@ static struct ids_vec *bpf_core_find_cands(const struct btf *local_btf,
                if (strncmp(local_name, targ_name, local_essent_len) == 0) {
                        pr_debug("[%d] %s: found candidate [%d] %s\n",
                                 local_type_id, local_name, i, targ_name);
-                       new_ids = realloc(cand_ids->data, cand_ids->len + 1);
+                       new_ids = reallocarray(cand_ids->data,
+                                              cand_ids->len + 1,
+                                              sizeof(*cand_ids->data));
                        if (!new_ids) {
                                err = -ENOMEM;
                                goto err_out;