From: Tycho Andersen <tycho@tycho.ws>
To: Andy Lutomirski <luto@amacapital.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>,
Kees Cook <keescook@chromium.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>
Subject: Re: [RFC 1/3] seccomp: add a return code to trap to userspace
Date: Sun, 4 Feb 2018 21:01:29 +0100 [thread overview]
Message-ID: <20180204200129.2bgq5yfaimg6xdg5@cisco> (raw)
In-Reply-To: <CALCETrWgu5n+SMqrsZQ7MVYPtzs8otuc7hpA5uPH+JNtFrMBkQ@mail.gmail.com>
Hi Andy,
On Sun, Feb 04, 2018 at 05:36:33PM +0000, Andy Lutomirski wrote:
> > The actual implementation of this is fairly small, although getting the
> > synchronization right was/is slightly complex. Also worth noting that there
> > is one race still present:
> >
> > 1. a task does a SECCOMP_RET_USER_NOTIF
> > 2. the userspace handler reads this notification
> > 3. the task dies
> > 4. a new task with the same pid starts
> > 5. this new task does a SECCOMP_RET_USER_NOTIF, gets the same cookie id
> > that the previous one did
> > 6. the userspace handler writes a response
>
> I'm slightly confused. I thought the id was never reused for a given
> struct seccomp_filter. (Also, shouldn't the id be u64, not u32?)
Well, what happens when u32/64 overflows? Eventually it will wrap.
> On very quick reading, I have a question. What happens if a process
> has two seccomp_filters attached, one of them returns
> SECCOMP_RET_USER_NOTIF, and the *other* one has a listener?
Good question, in seccomp_run_filters(), the first (lowest, last
applied) filter who returns SECCOMP_RET_USER_NOTIF is the one that
gets the notification and the other receives nothing.
I don't really have any reason to prefer this behavior, it's just what
happened without much thought.
Cheers,
Tycho
next prev parent reply other threads:[~2018-02-04 20:01 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-04 10:49 [RFC 0/3] seccomp trap to userspace Tycho Andersen
2018-02-04 10:49 ` [RFC 1/3] seccomp: add a return code to " Tycho Andersen
2018-02-04 17:36 ` Andy Lutomirski
2018-02-04 20:01 ` Tycho Andersen [this message]
2018-02-04 20:33 ` Andy Lutomirski
2018-02-05 8:47 ` Tycho Andersen
2018-02-13 21:09 ` Kees Cook
2018-02-14 15:29 ` Tycho Andersen
2018-02-14 17:19 ` Andy Lutomirski
2018-02-14 17:23 ` Tycho Andersen
2018-02-15 14:48 ` Christian Brauner
2018-02-27 0:49 ` Kees Cook
2018-02-27 3:27 ` Andy Lutomirski
2018-02-04 10:49 ` [RFC 2/3] seccomp: hoist out filter resolving logic Tycho Andersen
2018-02-13 21:29 ` Kees Cook
2018-02-14 15:33 ` Tycho Andersen
2018-02-04 10:49 ` [RFC 3/3] seccomp: add a way to get a listener fd from ptrace Tycho Andersen
2018-02-13 21:32 ` Kees Cook
2018-02-14 15:33 ` Tycho Andersen
2018-03-15 16:09 ` [RFC 0/3] seccomp trap to userspace Christian Brauner
2018-03-15 16:56 ` Andy Lutomirski
2018-03-15 17:05 ` Serge E. Hallyn
2018-03-15 17:11 ` Andy Lutomirski
2018-03-15 17:25 ` Christian Brauner
2018-03-15 17:30 ` Andy Lutomirski
2018-03-15 17:35 ` Tycho Andersen
2018-03-16 0:46 ` Andy Lutomirski
2018-03-16 14:47 ` Christian Brauner
2018-03-16 16:01 ` Andy Lutomirski
2018-03-16 16:40 ` Christian Brauner
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