linux-kernel - Re: [RFC PATCH v7 5/7] libbpf: Implement BTF type sorting validation for binary search optimization

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Message-ID: <e8f499647614e592845dbdfa23d53e6c62434485.camel@gmail.com>
Date: Fri, 21 Nov 2025 11:42:32 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Donglin Peng <dolinux.peng@...il.com>, Andrii Nakryiko
	 <andrii.nakryiko@...il.com>
Cc: ast@...nel.org, zhangxiaoqin@...omi.com, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, Donglin Peng <pengdonglin@...omi.com>, Alan Maguire
	 <alan.maguire@...cle.com>, Song Liu <song@...nel.org>
Subject: Re: [RFC PATCH v7 5/7] libbpf: Implement BTF type sorting
 validation for binary search optimization

On Thu, 2025-11-20 at 15:25 +0800, Donglin Peng wrote:

[...]

> Additionally, in the linear search branch, I saw there is a NULL check for
> the name returned by btf__name_by_offset. This suggests that checking
> name_off == 0 alone may not be sufficient to identify an anonymous type,
> which is why I used str_is_empty for a more robust check.

btf_str_by_offset(btf, offset) returns NULL only when 'offset' is
larger then 'btf->hdr.str_len'. However, function btf_check_meta()
verifies that this shall not happen by invoking
btf_name_offset_valid() check. The btf_check_meta() is invoked for all
types by btf_check_all_metas() called from btf_parse_base(),
btf_parse_module() and btf_parse_type_sec() -> btf_parse().

So, it appears that kernel protects itself from invalid name_off
values at BTF load time.

[...]