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libbpf: Improve sanity checking during BTF fix up

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If BTF is corrupted DATASEC's variable type ID might be incorrect.
Prevent this easy to detect situation with extra NULL check.
Reported by oss-fuzz project.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211103173213.1376990-3-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2021-11-03 10:32:10 -07:00 committed by Alexei Starovoitov
parent 833907876b
commit 88918dc12d
1 changed files with 2 additions and 3 deletions
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5
tools/lib/bpf/libbpf.c
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@ -2752,13 +2752,12 @@ static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
t_var = btf__type_by_id(btf, vsi->type);
var = btf_var(t_var);
if (!btf_is_var(t_var)) {
if (!t_var || !btf_is_var(t_var)) {
pr_debug("Non-VAR type seen in section %s\n", name);
return -EINVAL;
}
var = btf_var(t_var);
if (var->linkage == BTF_VAR_STATIC)
continue;