Re: [PATCH v12 bpf-next 6/8] btf: support kernel parsing of BTF with layout info

> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c

[ ... ]

> +static int btf_parse_layout_sec(struct btf_verifier_env *env)
> +{
> +	const struct btf_header *hdr = &env->btf->hdr;
> +	struct btf *btf = env->btf;
> +	void *start, *end;
> +
> +	if (hdr->hdr_len < sizeof(struct btf_header) ||
> +	    hdr->layout_len == 0)
> +		return 0;
> +
> +	/* Layout section must align to 4 bytes */
> +	if (hdr->layout_off & (sizeof(u32) - 1)) {
> +		btf_verifier_log(env, "Unaligned layout_off");
> +		return -EINVAL;
> +	}

When one of these validation errors fires, btf_verifier_log_hdr()
has already printed the header dump.  That function currently logs
type_off, type_len, str_off, and str_len, but not layout_off or
layout_len:

kernel/bpf/btf.c:btf_verifier_log_hdr() {
    ...
    __btf_verifier_log(log, "type_off: %u\n", hdr->type_off);
    __btf_verifier_log(log, "type_len: %u\n", hdr->type_len);
    __btf_verifier_log(log, "str_off: %u\n", hdr->str_off);
    __btf_verifier_log(log, "str_len: %u\n", hdr->str_len);
    __btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);
}

Should layout_off and layout_len be added to the header log, at
least when hdr_len >= sizeof(struct btf_header)?  Without them a
user who hits "Unaligned layout_off" or "Layout section is too
small" cannot see the actual values in the verifier output.

> +	start = btf->nohdr_data + hdr->layout_off;
> +	end = start + hdr->layout_len;
> +
> +	if (hdr->layout_len < sizeof(struct btf_layout)) {
> +		btf_verifier_log(env, "Layout section is too small");
> +		return -EINVAL;
> +	}
> +	if (hdr->layout_len % sizeof(struct btf_layout) != 0) {
> +		btf_verifier_log(env, "layout_len is not multiple of %zu",
> +				 sizeof(struct btf_layout));
> +		return -EINVAL;
> +	}
> +	if (end > btf->data + btf->data_size) {
> +		btf_verifier_log(env, "Layout section is too big");
> +		return -EINVAL;
> +	}
> +	btf->layout = start;
> +
> +	return 0;
> +}


---
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