From: Tycho Andersen <tycho@tycho.ws>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Linux API <linux-api@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"Serge E . Hallyn" <serge@hallyn.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
Tyler Hicks <tyhicks@canonical.com>,
Akihiro Suda <suda.akihiro@lab.ntt.co.jp>,
Jann Horn <jannh@google.com>
Subject: Re: [PATCH v6 4/5] seccomp: add support for passing fds via USER_NOTIF
Date: Thu, 13 Sep 2018 03:25:44 -0600 [thread overview]
Message-ID: <20180913092544.GC4672@cisco> (raw)
In-Reply-To: <CALCETrWZmN4FeCSwemfMeayupBmQ-NqpVWQuqSU34CLvzdx8gw@mail.gmail.com>
On Wed, Sep 12, 2018 at 04:52:38PM -0700, Andy Lutomirski wrote:
> On Thu, Sep 6, 2018 at 8:28 AM, Tycho Andersen <tycho@tycho.ws> wrote:
> > The idea here is that the userspace handler should be able to pass an fd
> > back to the trapped task, for example so it can be returned from socket().
> >
> > I've proposed one API here, but I'm open to other options. In particular,
> > this only lets you return an fd from a syscall, which may not be enough in
> > all cases. For example, if an fd is written to an output parameter instead
> > of returned, the current API can't handle this. Another case is that
> > netlink takes as input fds sometimes (IFLA_NET_NS_FD, e.g.). If netlink
> > ever decides to install an fd and output it, we wouldn't be able to handle
> > this either.
>
> An alternative could be to have an API (an ioctl on the listener,
> perhaps) that just copies an fd into the tracee. There would be the
> obvious set of options: do we replace an existing fd or allocate a new
> one, and is it CLOEXEC. Then the tracer could add an fd and then
> return it just like it's a regular number.
>
> I feel like this would be more flexible and conceptually simpler, but
> maybe a little slower for the common cases. What do you think?
Yes, I like this. It also future (or current-) proofs the API against
instances where we return an FD in a structure and not via the return
code of the syscall.
Tycho
next prev parent reply other threads:[~2018-09-13 9:25 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 15:28 [PATCH v6 0/5] seccomp trap to userspace Tycho Andersen
2018-09-06 15:28 ` [PATCH v6 1/5] seccomp: add a return code to " Tycho Andersen
2018-09-06 22:15 ` Tyler Hicks
2018-09-07 15:45 ` Tycho Andersen
2018-09-08 20:35 ` Tycho Andersen
2018-09-06 15:28 ` [PATCH v6 2/5] seccomp: make get_nth_filter available outside of CHECKPOINT_RESTORE Tycho Andersen
2018-09-11 10:25 ` kbuild test robot
2018-09-06 15:28 ` [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace Tycho Andersen
2018-09-06 15:45 ` Jann Horn
2018-09-06 15:50 ` Tycho Andersen
2018-09-13 0:00 ` Andy Lutomirski
2018-09-13 9:24 ` Tycho Andersen
2018-10-17 7:25 ` Michael Tirado
2018-10-17 15:00 ` Tycho Andersen
[not found] ` <CAMkWEXM1c7AGTH=tpgoHtPnFFY-V+05nGOU90Sa1E3EPY9OhKQ@mail.gmail.com>
2018-10-17 18:15 ` Michael Tirado
2018-10-21 16:00 ` Tycho Andersen
2018-10-17 18:31 ` Kees Cook
2018-09-06 15:28 ` [PATCH v6 4/5] seccomp: add support for passing fds via USER_NOTIF Tycho Andersen
2018-09-06 16:15 ` Jann Horn
2018-09-06 16:22 ` Tycho Andersen
2018-09-06 18:30 ` Tycho Andersen
2018-09-10 17:00 ` Jann Horn
2018-09-11 20:29 ` Tycho Andersen
2018-09-12 23:52 ` Andy Lutomirski
2018-09-13 9:25 ` Tycho Andersen [this message]
2018-09-13 9:42 ` Aleksa Sarai
2018-09-19 9:55 ` Tycho Andersen
2018-09-19 14:19 ` Andy Lutomirski
2018-09-19 14:38 ` Tycho Andersen
2018-09-19 19:58 ` Andy Lutomirski
2018-09-20 23:42 ` Tycho Andersen
2018-09-21 2:18 ` Andy Lutomirski
2018-09-21 13:39 ` Tycho Andersen
2018-09-21 18:27 ` Andy Lutomirski
2018-09-21 22:03 ` Tycho Andersen
2018-09-21 20:46 ` Jann Horn
2018-09-25 12:53 ` Tycho Andersen
2018-09-06 15:28 ` [PATCH v6 5/5] samples: add an example of seccomp user trap Tycho Andersen
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