linux-kernel - Re: [PATCH bpf-next 0/4] Introduce bpf_kernfs_read

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Message-ID: <4B2C62F3-FF40-4227-A06B-AE575F889D19@meta.com>
Date: Thu, 19 Jun 2025 15:31:32 +0000
From: Song Liu <songliubraving@...a.com>
To: Christian Brauner <brauner@...nel.org>
CC: Tejun Heo <tj@...nel.org>, Song Liu <song@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org"
	<linux-fsdevel@...r.kernel.org>,
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	<linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org"
	<linux-security-module@...r.kernel.org>,
        Kernel Team <kernel-team@...a.com>,
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        "eddyz87@...il.com"
	<eddyz87@...il.com>,
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        "gregkh@...uxfoundation.org"
	<gregkh@...uxfoundation.org>,
        "daan.j.demeyer@...il.com"
	<daan.j.demeyer@...il.com>
Subject: Re: [PATCH bpf-next 0/4] Introduce bpf_kernfs_read_xattr



> On Jun 19, 2025, at 1:48 AM, Christian Brauner <brauner@...nel.org> wrote:
> 
> On Wed, Jun 18, 2025 at 02:43:34PM -1000, Tejun Heo wrote:
>> Hello,
>> 
>> On Wed, Jun 18, 2025 at 04:37:35PM -0700, Song Liu wrote:
>>> Introduce a new kfunc bpf_kernfs_read_xattr, which can read xattr from
>>> kernfs nodes (cgroupfs, for example). The primary users are LSMs, for
>>> example, from systemd. sched_ext could also use xattrs on cgroupfs nodes.
>>> However, this is not allowed yet, because bpf_kernfs_read_xattr is only
>>> allowed from LSM hooks. The plan is to address sched_ext later (or in a
>>> later revision of this set).
>> 
>> I don't think kernfs is the name we should be exposing to BPF users. This is
>> an implementation detail which may change in the future. I'd rather make it
>> a generic interface or a cgroup specific one. The name "kernfs" doesn't
> 
> cgroup specific, please. That's what I suggested to Daan.

I guess there was some misunderstanding. I will make this cgroup specific 
in v2. 

Thanks,
Song