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    Subject[PATCH AUTOSEL 5.16 009/217] libbpf: Improve sanity checking during BTF fix up
    Date
    From: Andrii Nakryiko <andrii@kernel.org>

    [ Upstream commit 88918dc12dc357a06d8d722a684617b1c87a4654 ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/lib/bpf/libbpf.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
    index b5bf1c074832e..18651e11b9ba3 100644
    --- a/tools/lib/bpf/libbpf.c
    +++ b/tools/lib/bpf/libbpf.c
    @@ -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;

    --
    2.34.1
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