linux-kernel - Re: [PATCH v5 bpf-next 0/5] bpf path iterator

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Message-ID: <20250624.xahShi0iCh7t@digikod.net>
Date: Tue, 24 Jun 2025 20:45:58 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Song Liu <song@...nel.org>
Cc: bpf@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, brauner@...nel.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, m@...wtm.org, neil@...wn.name, 
	Günther Noack <gnoack@...gle.com>
Subject: Re: [PATCH v5 bpf-next 0/5] bpf path iterator

On Fri, Jun 20, 2025 at 02:59:17PM -0700, Song Liu wrote:
> Hi Christian, Mickaël, and folks,
> 
> Could you please share your comments on this version? Does this
> look sane?

This looks good to me but we need to know what is the acceptable next
step to support RCU.  If we can go with another _rcu helper, I'm good
with the current approach, otherwise we need to figure out a way to
leverage the current helper to make it compatible with callers being in
a RCU read-side critical section while leveraging safe path walk (i.e.
several calls to path_walk_parent).

> 
> Thanks,
> Song
> 
> On Mon, Jun 16, 2025 at 11:11 PM Song Liu <song@...nel.org> wrote:
> >
> > In security use cases, it is common to apply rules to VFS subtrees.
> > However, filtering files in a subtree is not straightforward [1].
> >
> > One solution to this problem is to start from a path and walk up the VFS
> > tree (towards the root). Among in-tree LSMs, Landlock uses this solution.
> >
> 
> [...]
>