libbpf: Tighten BTF type ID rewriting with error checking

mainline inclusion
from mainline-5.13-rc1
commit 83a15727
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=83a157279f2125ce1c4d6d93750440853746dff0

-------------------------------------------------

It should never fail, but if it does, it's better to know about this rather
than end up with nonsensical type IDs.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-11-andrii@kernel.org
(cherry picked from commit 83a15727)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/linker.c

@@ -1429,6 +1429,13 @@ static int linker_fixup_btf(struct src_obj *obj)
 static int remap_type_id(__u32 *type_id, void *ctx)
 {
 	int *id_map = ctx;
+	int new_id = id_map[*type_id];
+
+	/* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
+	if (new_id == 0 && *type_id != 0) {
+		pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id);
+		return -EINVAL;
+	}
 
 	*type_id = id_map[*type_id];