LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Daniel Colascione <dancol@google.com>
To: Christian Brauner <christian@brauner.io>
Cc: Aleksa Sarai <cyphar@cyphar.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Jann Horn <jannh@google.com>, Andy Lutomirski <luto@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	Tim Murray <timmurray@google.com>,
	linux-man <linux-man@vger.kernel.org>,
	Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH v1 2/2] signal: add procfd_signal() syscall
Date: Mon, 19 Nov 2018 13:41:21 -0800
Message-ID: <CAKOZueup5L9Fd=tTK5g1415x0muLP_cPkxf4o26-kCPtH_caqw@mail.gmail.com> (raw)
In-Reply-To: <20181119213722.z54huio5g4kuldxk@brauner.io>

On Mon, Nov 19, 2018 at 1:37 PM Christian Brauner <christian@brauner.io> wrote:
>
> On Mon, Nov 19, 2018 at 01:26:22PM -0800, Daniel Colascione wrote:
> > On Mon, Nov 19, 2018 at 1:21 PM, Christian Brauner <christian@brauner.io> wrote:
> > > That can be done without a loop by comparing the level counter for the
> > > two pid namespaces.
> > >
> > >>
> > >> And you can rewrite pidns_get_parent to use it. So you would instead be
> > >> doing:
> > >>
> > >>     if (pidns_is_descendant(proc_pid_ns, task_active_pid_ns(current)))
> > >>         return -EPERM;
> > >>
> > >> (Or you can just copy the 5-line loop into procfd_signal -- though I
> > >> imagine we'll need this for all of the procfd_* APIs.)
> >
> > Why is any of this even necessary? Why does the child namespace we're
> > considering even have a file descriptor to its ancestor's procfs? If
>
> Because you can send file descriptors between processes and container
> runtimes tend to do that.

Right. But why *would* a container runtime send one of these procfs
FDs to a container?

> > it has one of these FDs, it can already *read* all sorts of
> > information it really shouldn't be able to acquire, so the additional
> > ability to send a signal (subject to the usual permission checks)
> > feels like sticking a finger in a dike that's already well-perforated.
> > IMHO, we shouldn't bother with this check. The patch would be simpler
> > without it.
>
> We will definitely not allow signaling processes in an ancestor pid
> namespace! That is a security issue! I can imagine container runtimes
> killing their monitoring process etc. pp. Not happening, unless someone
> with deep expertise in signals can convince me otherwise.

If parent namespace procfs FDs or mounts really can leak into child
namespaces as easily as Aleksa says, then I don't mind adding the
check. I was under the impression that if you find yourself in this
situation, you already have a big problem.

  reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-19 10:32 [PATCH v1 0/2] proc: allow signaling processes via file descriptors Christian Brauner
2018-11-19 10:32 ` [PATCH v1 1/2] proc: get process file descriptor from /proc/<pid> Christian Brauner
2018-11-19 15:32   ` Andy Lutomirski
2018-11-19 18:20     ` Christian Brauner
2018-11-19 10:32 ` [PATCH v1 2/2] signal: add procfd_signal() syscall Christian Brauner
2018-11-19 15:45   ` Andy Lutomirski
2018-11-19 15:57     ` Daniel Colascione
2018-11-19 18:39     ` Christian Brauner
2018-11-19 15:59   ` Daniel Colascione
2018-11-19 18:29     ` Christian Brauner
2018-11-19 19:02       ` Eric W. Biederman
2018-11-19 19:31         ` Christian Brauner
2018-11-19 19:39           ` Daniel Colascione
2018-11-19 17:10   ` Eugene Syromiatnikov
2018-11-19 18:23     ` Christian Brauner
2018-11-19 17:14   ` Eugene Syromiatnikov
2018-11-19 20:28   ` Aleksa Sarai
2018-11-19 20:55     ` Christian Brauner
2018-11-19 21:13       ` Christian Brauner
2018-11-19 21:18       ` Aleksa Sarai
2018-11-19 21:20         ` Christian Brauner
2018-11-19 21:21         ` Christian Brauner
2018-11-19 21:25           ` Aleksa Sarai
2018-11-19 21:26           ` Daniel Colascione
2018-11-19 21:36             ` Aleksa Sarai
2018-11-19 21:37             ` Christian Brauner
2018-11-19 21:41               ` Daniel Colascione [this message]
2018-11-20  4:59                 ` Eric W. Biederman
2018-11-20 10:31                   ` Christian Brauner
2018-11-21 21:39                     ` Serge E. Hallyn
2018-11-19 21:23         ` Aleksa Sarai
2018-11-22  7:41           ` Serge E. Hallyn
2018-11-19 22:39   ` Tycho Andersen
2018-11-19 22:49     ` Daniel Colascione
2018-11-19 23:07       ` Tycho Andersen
2018-11-20  0:27         ` Andy Lutomirski
2018-11-20  0:32           ` Christian Brauner
2018-11-20  0:34             ` Andy Lutomirski
2018-11-20  0:49           ` Daniel Colascione
2018-11-22  7:48     ` Serge E. Hallyn
2018-11-19 23:35   ` kbuild test robot
2018-11-19 23:37   ` kbuild test robot
2018-11-19 23:45     ` Christian Brauner
2018-11-28 21:45   ` Joey Pabalinas
2018-11-28 22:05     ` Christian Brauner
2018-11-28 23:02       ` Joey Pabalinas
2018-11-19 10:32 ` [PATCH] procfd_signal.2: document procfd_signal syscall Christian Brauner
2018-11-20 13:29   ` Michael Kerrisk (man-pages)
2018-11-28 20:59   ` Florian Weimer
2018-11-28 21:12     ` Christian Brauner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAKOZueup5L9Fd=tTK5g1415x0muLP_cPkxf4o26-kCPtH_caqw@mail.gmail.com' \
    --to=dancol@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=christian@brauner.io \
    --cc=cyphar@cyphar.com \
    --cc=ebiederm@xmission.com \
    --cc=jannh@google.com \
    --cc=keescook@chromium.org \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-man@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=oleg@redhat.com \
    --cc=serge@hallyn.com \
    --cc=timmurray@google.com \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git