From: Al Viro <viro@zeniv.linux.org.uk>
To: John Ericson <mail@johnericson.me>
Cc: Andy Lutomirski <luto@kernel.org>, Li Chen <me@linux.beauty>,
Cong Wang <cwang@multikernel.io>,
Christian Brauner <brauner@kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Jan Kara <jack@suse.cz>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Kees Cook <kees@kernel.org>,
Sergei Zimmerman <sergei@zimmerman.foo>,
Farid Zakaria <farid.m.zakaria@gmail.com>
Subject: Re: [RFC] Null Namespaces
Date: Thu, 25 Jun 2026 02:10:23 +0100 [thread overview]
Message-ID: <20260625011023.GM2636677@ZenIV> (raw)
In-Reply-To: <103524f8-1658-41df-88e9-cf49c628a721@app.fastmail.com>
On Wed, Jun 24, 2026 at 07:53:53PM -0400, John Ericson wrote:
> I wanted to discuss a bit about each type of namespace to indicate that
> this is a concept I think works across the board --- it wouldn't be such
> a good solution for the process spawning API if it was only applicable
> to some but not all namespace types. But the truth is that I have
> thought about the FS cases the most, as I think you have picked up on.
>
> If there is interest in landing
>
> 1. null CWD
> 2. null root fs
> 3. null mount namespace
>
> in isolation, and then returning to the other namespaces to iron out
> their details, that would be fantastic. It would be much nicer for me to
> get some momentum that way, without having to design everything all at
> once first before getting to implement anything.
Please, start with explaining what, in your opinion, a mount namespace _is_,
and where does "mount X is attached at path P relative to mount Y" belong.
What's the fundamental difference between CWD and any open descriptor for
a directory? Why does it make sense to ban the former, but allow the
equivalents done via the latter?
next prev parent reply other threads:[~2026-06-25 1:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-24 22:51 [RFC] Null Namespaces John Ericson
2026-06-24 23:06 ` Andy Lutomirski
2026-06-24 23:20 ` Andy Lutomirski
2026-06-24 23:53 ` John Ericson
2026-06-25 1:10 ` Al Viro [this message]
2026-06-25 3:41 ` John Ericson
2026-06-24 23:12 ` Al Viro
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