linux-kernel - Re: [PATCH v5 bpf-next 2/5] landlock: Use path_walk

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Message-ID: <C62BF1A0-8A3C-4B58-8CC8-5BD1A17B1BDB@meta.com>
Date: Thu, 3 Jul 2025 22:27:02 +0000
From: Song Liu <songliubraving@...a.com>
To: Mickaël Salaün <mic@...ikod.net>
CC: Song Liu <song@...nel.org>, "brauner@...nel.org" <brauner@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org"
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        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org"
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        Kernel Team <kernel-team@...a.com>,
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        Günther Noack <gnoack@...gle.com>,
        Jann Horn
	<jannh@...gle.com>
Subject: Re: [PATCH v5 bpf-next 2/5] landlock: Use path_walk_parent()

Hi Mickaël,

> On Jul 3, 2025, at 11:29 AM, Mickaël Salaün <mic@...ikod.net> wrote:
> 
> On Mon, Jun 16, 2025 at 11:11:13PM -0700, Song Liu wrote:
>> Use path_walk_parent() to walk a path up to its parent.
>> 
>> No functional changes intended.
> 
> Using this helper actualy fixes the issue highlighted by Al.  Even if it
> was reported after the first version of this patch series, the issue
> should be explained in the commit message and these tags should be
> added:
> 
> Reported-by: Al Viro <viro@...iv.linux.org.uk>
> Closes: https://lore.kernel.org/r/20250529231018.GP2023217@ZenIV 
> Fixes: cb2c7d1a1776 ("landlock: Support filesystem access-control")
> 
> I like this new helper but we should have a clear plan to be able to
> call such helper in a RCU read-side critical section before we merge
> this series.  We're still waiting for Christian.
> 
> I sent a patch to fix the handling of disconnected directories for
> Landlock, and it will need to be backported:
> https://lore.kernel.org/all/20250701183812.3201231-1-mic@digikod.net/
> Unfortunately a rebase would be needed for the path_walk_parent patch,
> but I can take it in my tree if everyone is OK.

The fix above also touches VFS code (makes path_connected available 
out of namei.c. It probably should also go through VFS tree? 

Maybe you can send 1/5 and 2/5 of this set (with necessary changes) 
and your fix together to VFS tree. Then, I will see how to route the
BPF side patches. 

Thanks,
Song