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

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Message-ID: <20250619-zwirn-thunfisch-de6e4891a453@brauner>
Date: Thu, 19 Jun 2025 10:48:13 +0200
From: Christian Brauner <brauner@...nel.org>
To: Tejun Heo <tj@...nel.org>
Cc: Song Liu <song@...nel.org>, bpf@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, kernel-team@...a.com, andrii@...nel.org, eddyz87@...il.com, 
	ast@...nel.org, daniel@...earbox.net, martin.lau@...ux.dev, 
	viro@...iv.linux.org.uk, jack@...e.cz, kpsingh@...nel.org, mattbobrowski@...gle.com, 
	amir73il@...il.com, gregkh@...uxfoundation.org, daan.j.demeyer@...il.com
Subject: Re: [PATCH bpf-next 0/4] Introduce bpf_kernfs_read_xattr

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.