Re: [PATCH bpf-next v2] libbpf: Check for unknown type ID in btf__align_of()

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Sat Sep 19, 2026 at 5:45 PM UTC, Abhinav Madake wrote:
> btf__align_of() passes the result of btf__type_by_id() to btf_kind()
> without a NULL check, so an unknown type ID crashes. Parsed BTF cannot
> hit this since btf_sanity_check() rejects dangling references, but BTF
> built with btf__add_*() can, as those only check the ID range.
>
> Return 0 with errno set to EINVAL, like the unsupported-kind case.
>
> Link: https://github.com/libbpf/libbpf/issues/983
> Signed-off-by: Abhinav Madake <abhinavmadake@gmail.com>
> ---
> v2: return 0 with errno instead of -EINVAL, callers test for 0.
>
>  tools/lib/bpf/btf.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 908bd3442..6bfbc7a65 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -986,8 +986,12 @@ done:
>  int btf__align_of(const struct btf *btf, __u32 id)
>  {
>  	const struct btf_type *t = btf__type_by_id(btf, id);
> -	__u16 kind = btf_kind(t);
> +	__u16 kind;
>  
> +	if (!t)
> +		return errno = EINVAL, 0;

We don't do defensive programming in libbpf.
input is trusted.

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