linux-kernel - Re: [PATCH bpf-next v4 0/4] Use correct destructor kfunc types

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Message-ID: <1fd29f17-a0e9-4032-8349-a85c9659a5f2@redhat.com>
Date: Fri, 9 Jan 2026 09:52:12 +0100
From: Viktor Malik <vmalik@...hat.com>
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>, Martin KaFai Lau
 <martin.lau@...ux.dev>, 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>,
 Network Development <netdev@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
 Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH bpf-next v4 0/4] Use correct destructor kfunc types

On 1/5/26 17:16, Alexei Starovoitov wrote:
> On Mon, Jan 5, 2026 at 5:56 AM Viktor Malik <vmalik@...hat.com> wrote:
>>
>> On 11/26/25 23:17, 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.
>>
>> Hi,
>>
>> this seems to have slipped through the cracks so I'm bumping the thread.
>> It would be nice if we could merge this.
> 
> It did. Please rebase, resend.

@Sami, could you please rebase and resend?

Thanks!

>