From: Ian Kent <raven@themaw.net>
To: Christian Brauner <christian@brauner.io>
Cc: David Howells <dhowells@redhat.com>,
keyrings@vger.kernel.org, trond.myklebust@hammerspace.com,
sfrench@samba.org,
James Bottomley <James.Bottomley@HansenPartnership.com>,
linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org,
containers@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [RFC PATCH 02/27] containers: Implement containers as kernel objects
Date: Thu, 21 Feb 2019 18:39:28 +0800 [thread overview]
Message-ID: <6c907b21aca7b93c3b637ba0e30de4c6acb356f4.camel@themaw.net> (raw)
In-Reply-To: <20190220132600.c5ahsmnoihdrcqeq@brauner.io>
On Wed, 2019-02-20 at 14:26 +0100, Christian Brauner wrote:
> On Wed, Feb 20, 2019 at 10:46:24AM +0800, Ian Kent wrote:
> > On Fri, 2019-02-15 at 16:07 +0000, David Howells wrote:
> > > Implement a kernel container object such that it contains the following
> > > things:
> > >
> > > (1) Namespaces.
> > >
> > > (2) A root directory.
> > >
> > > (3) A set of processes, including one designated as the 'init' process.
> >
> > Yeah, I think a name other than init needs to be used for this
> > process.
> >
> > The problem being that there is no requirement for container
> > process 1 to behave in any way like an "init" process is
> > expected to behave and that leads to confusion (at least
> > it certainly did for me).
>
> If you look at the documentation for pid namespaces(7) you can see that
> the pid 1 inside a pid namespace is expected to behave like an init
> process:
> - "The first process created in a new namespace [...] has the PID 1,
> and is the "init" process for the namespace (see init(1))."
> - "[...] child process that is orphaned within the namespace will be
> reparented to this process rather than init(1) [...]"
> - "If the "init" process of a PID namespace terminates, the kernel
> terminates all of the processes in the namespace via a SIGKILL
> signal. This behavior reflects the fact that the "init" process is
> essential for the cor‐ rect operation of a PID namespace."
> - "Only signals for which the "init" process has established a signal
> handler can be sent to the "init" process by other members of the
> PID namespace."
> - "[...] the reboot(2) system call causes a signal to be sent to the
> namespace "init" process."
>
> This is one of the reasons why all major current container runtimes
> finally after years of failing to realize this run a stub init process
> that mimicks a dumb init. Sure, you get away with not having an init
> that behaves like an init but this is inherently broken or at least
> against the way pid namespaces were designed.
TBH I wasn't sure why the signal I sent didn't arrive, AFAICS
it should have regardless of what signals the container init
process was accepting. But it could have been due to a
different problem in my kernel code (that's very likely).
In any case it wasn't worth perusing because even if I did work
it out I had already found that the request_key sub-system wasn't
playing well with others when trying to run something within a
container's namespaces, so no point in going further ...
Ian
next prev parent reply other threads:[~2019-02-21 10:39 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 16:07 [RFC PATCH 00/27] Containers and using authenticated filesystems David Howells
2019-02-15 16:07 ` [RFC PATCH 01/27] containers: Rename linux/container.h to linux/container_dev.h David Howells
2019-02-15 16:07 ` [RFC PATCH 02/27] containers: Implement containers as kernel objects David Howells
2019-02-17 18:57 ` Trond Myklebust
2019-02-17 19:39 ` James Bottomley
2019-02-19 16:56 ` Eric W. Biederman
2019-02-19 23:03 ` David Howells
2019-02-20 14:23 ` Trond Myklebust
2019-02-19 23:06 ` David Howells
2019-02-20 2:20 ` James Bottomley
2019-02-20 3:04 ` Ian Kent
2019-02-20 3:46 ` James Bottomley
2019-02-20 4:42 ` Ian Kent
2019-02-20 6:57 ` Paul Moore
2019-02-19 23:13 ` David Howells
2019-02-19 23:55 ` Tycho Andersen
2019-02-20 2:46 ` Ian Kent
2019-02-20 13:26 ` Christian Brauner
2019-02-21 10:39 ` Ian Kent [this message]
2019-02-15 16:07 ` [RFC PATCH 03/27] containers: Provide /proc/containers David Howells
2019-02-15 16:07 ` [RFC PATCH 04/27] containers: Allow a process to be forked into a container David Howells
2019-02-15 17:39 ` Stephen Smalley
2019-02-19 16:39 ` Eric W. Biederman
2019-02-19 23:16 ` David Howells
2019-02-15 16:07 ` [RFC PATCH 05/27] containers: Open a socket inside " David Howells
2019-02-19 16:41 ` Eric W. Biederman
2019-02-15 16:08 ` [RFC PATCH 06/27] containers, vfs: Allow syscall dirfd arguments to take a container fd David Howells
2019-02-19 16:45 ` Eric W. Biederman
2019-02-19 23:24 ` David Howells
2019-02-15 16:08 ` [RFC PATCH 07/27] containers: Make fsopen() able to create a superblock in a container David Howells
2019-02-15 16:08 ` [RFC PATCH 08/27] containers, vfs: Honour CONTAINER_NEW_EMPTY_FS_NS David Howells
2019-02-17 0:11 ` Al Viro
2019-02-15 16:08 ` [RFC PATCH 09/27] vfs: Allow mounting to other namespaces David Howells
2019-02-17 0:14 ` Al Viro
2019-02-15 16:08 ` [RFC PATCH 10/27] containers: Provide fs_context op for container setting David Howells
2019-02-15 16:09 ` [RFC PATCH 11/27] containers: Sample program for driving container objects David Howells
2019-02-15 16:09 ` [RFC PATCH 12/27] containers: Allow a daemon to intercept request_key upcalls in a container David Howells
2019-02-15 16:09 ` [RFC PATCH 13/27] keys: Provide a keyctl to query a request_key authentication key David Howells
2019-02-15 16:09 ` [RFC PATCH 14/27] keys: Break bits out of key_unlink() David Howells
2019-02-15 16:09 ` [RFC PATCH 15/27] keys: Make __key_link_begin() handle lockdep nesting David Howells
2019-02-15 16:09 ` [RFC PATCH 16/27] keys: Grant Link permission to possessers of request_key auth keys David Howells
2019-02-15 16:10 ` [RFC PATCH 17/27] keys: Add a keyctl to move a key between keyrings David Howells
2019-02-15 16:10 ` [RFC PATCH 18/27] keys: Find the least-recently used unseen key in a keyring David Howells
2019-02-15 16:10 ` [RFC PATCH 19/27] containers: Sample: request_key upcall handling David Howells
2019-02-15 16:10 ` [RFC PATCH 20/27] container, keys: Add a container keyring David Howells
2019-02-15 21:46 ` Eric Biggers
2019-02-15 16:11 ` [RFC PATCH 21/27] keys: Fix request_key() lack of Link perm check on found key David Howells
2019-02-15 16:11 ` [RFC PATCH 22/27] KEYS: Replace uid/gid/perm permissions checking with an ACL David Howells
2019-02-15 17:32 ` Stephen Smalley
2019-02-15 17:39 ` David Howells
2019-02-15 16:11 ` [RFC PATCH 23/27] KEYS: Provide KEYCTL_GRANT_PERMISSION David Howells
2019-02-15 16:11 ` [RFC PATCH 24/27] keys: Allow a container to be specified as a subject in a key's ACL David Howells
2019-02-15 16:11 ` [RFC PATCH 25/27] keys: Provide a way to ask for the container keyring David Howells
2019-02-15 16:12 ` [RFC PATCH 26/27] keys: Allow containers to be included in key ACLs by name David Howells
2019-02-15 16:12 ` [RFC PATCH 27/27] containers: Sample to grant access to a key in a container David Howells
2019-02-15 22:36 ` [RFC PATCH 00/27] Containers and using authenticated filesystems James Morris
2019-02-19 16:35 ` Eric W. Biederman
2019-02-20 14:18 ` Christian Brauner
2019-02-19 23:42 ` David Howells
2019-02-20 7:00 ` Paul Moore
2019-02-20 18:54 ` Steve French
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