From: Christian Brauner <christian@brauner.io> To: Daniel Colascione <dancol@google.com> 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 22:37:24 +0100 [thread overview] Message-ID: <20181119213722.z54huio5g4kuldxk@brauner.io> (raw) In-Reply-To: <CAKOZuevEx6CbcxrR8eVZrUXDcN5y1GPsXdSoHfQteSQKypx0qw@mail.gmail.com> 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. > 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.
next prev parent reply other threads:[~2018-11-19 21:37 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 [this message] 2018-11-19 21:41 ` Daniel Colascione 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=20181119213722.z54huio5g4kuldxk@brauner.io \ --to=christian@brauner.io \ --cc=akpm@linux-foundation.org \ --cc=cyphar@cyphar.com \ --cc=dancol@google.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 \ --subject='Re: [PATCH v1 2/2] signal: add procfd_signal() syscall' \ /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
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).