netdev - Re: [PATCH bpf-next v5 0/4] Use correct destructor kfunc types

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Message-ID: <a71a2980-9814-4f94-875b-cd6da6822a31@linux.dev>
Date: Mon, 12 Jan 2026 12:33:15 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>,
 Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 Viktor Malik <vmalik@...hat.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v5 0/4] Use correct destructor kfunc types

On 1/10/26 12:25 AM, Sami Tolvanen wrote:
> Hi folks,
> 
> While running BPF self-tests with CONFIG_CFI (Control Flow
> Integrity) enabled, I ran into a couple of failures in
> bpf_obj_free_fields() caused by type mismatches between the
> btf_dtor_kfunc_t function pointer type and the registered
> destructor functions.
> 
> It looks like we can't change the argument type for these
> functions to match btf_dtor_kfunc_t because the verifier doesn't
> like void pointer arguments for functions used in BPF programs,
> so this series fixes the issue by adding stubs with correct types
> to use as destructors for each instance of this I found in the
> kernel tree.
> 
> The last patch changes btf_check_dtor_kfuncs() to enforce the
> function type when CFI is enabled, so we don't end up registering
> destructors that panic the kernel.

Acked-by: Martin KaFai Lau <martin.lau@...nel.org>