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 [thread overview]
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.
next prev parent reply other threads:[~2018-11-19 21:41 UTC|newest]
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
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