From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org,
Christian Brauner <christian@brauner.io>, Jan Kara <jack@suse.cz>,
"H. Peter Anvin" <hpa@zytor.com>,
Werner Almesberger <werner@almesberger.net>
Subject: Re: [RFC] pivot_root(2) races
Date: Thu, 12 Feb 2026 19:22:54 +0000 [thread overview]
Message-ID: <20260212192254.GO3183987@ZenIV> (raw)
In-Reply-To: <CAHk-=wikNJ82dh097VZbqNf_jAiwwZ_opzfvMr-8Ub3_1cx3jQ@mail.gmail.com>
On Sun, Feb 08, 2026 at 10:44:31PM -0800, Linus Torvalds wrote:
>
> Am I mis-reading things entirely, or can a random process in that
> container (that has mount permissions in that thing) basically do
> pivot_root(), and in the process change the CWD of that root process
> that just happens to be looking at that container state?
They can. But then they can do other fun things to the environment
there, so naive root process walking in might be in for really
unpleasant things. Creating use of mount --move, for example. Or
umount -l, or...
We could restrict the set of those who could be flipped, but I doubt
that "could ptrace" is workable - that would exclude all kernel threads,
and that could easily break existing setups in hard-to-recover ways.
next prev parent reply other threads:[~2026-02-12 19:20 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-09 0:34 [RFC] pivot_root(2) races Al Viro
2026-02-09 5:49 ` Linus Torvalds
2026-02-09 5:53 ` H. Peter Anvin
2026-02-09 6:34 ` Al Viro
2026-02-09 6:44 ` Linus Torvalds
2026-02-09 11:53 ` Christian Brauner
2026-02-12 17:17 ` Askar Safin
2026-02-12 19:11 ` Linus Torvalds
2026-02-12 19:31 ` H. Peter Anvin
2026-02-13 9:51 ` Aleksa Sarai
2026-02-13 17:47 ` Askar Safin
2026-02-13 20:27 ` H. Peter Anvin
2026-02-13 20:35 ` H. Peter Anvin
2026-02-13 22:25 ` Al Viro
2026-02-13 23:00 ` H. Peter Anvin
2026-02-13 23:41 ` Al Viro
2026-02-13 23:40 ` H. Peter Anvin
2026-02-14 12:42 ` Christian Brauner
2026-02-15 0:48 ` H. Peter Anvin
2026-02-17 8:37 ` Christian Brauner
2026-02-14 16:20 ` Askar Safin
2026-02-15 0:49 ` H. Peter Anvin
2026-02-13 13:46 ` Aleksa Sarai
2026-02-13 15:03 ` H. Peter Anvin
2026-02-13 17:47 ` Linus Torvalds
2026-02-13 18:27 ` Askar Safin
2026-02-13 18:39 ` Linus Torvalds
2026-02-13 20:00 ` H. Peter Anvin
2026-02-14 15:31 ` Askar Safin
2026-02-15 0:52 ` H. Peter Anvin
2026-02-14 12:15 ` Christian Brauner
2026-02-14 16:18 ` Linus Torvalds
2026-02-14 17:40 ` Al Viro
2026-02-17 8:35 ` Christian Brauner
2026-02-13 18:42 ` H. Peter Anvin
2026-02-13 20:08 ` H. Peter Anvin
2026-02-12 19:22 ` Al Viro [this message]
2026-02-13 17:34 ` Askar Safin
2026-02-13 22:28 ` Al Viro
2026-02-14 16:16 ` Askar Safin
2026-02-12 13:23 ` Askar Safin
2026-02-12 19:25 ` Al Viro
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