From: Jann Horn <jannh@google.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: kernel list <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>,
Andy Lutomirski <luto@kernel.org>,
Tycho Andersen <tycho@tycho.ws>,
Matt Denton <mpdenton@google.com>,
Sargun Dhillon <sargun@sargun.me>,
Chris Palmer <palmer@google.com>,
Aleksa Sarai <cyphar@cyphar.com>,
Robert Sesek <rsesek@google.com>,
Jeffrey Vander Stoep <jeffv@google.com>,
Linux Containers <containers@lists.linux-foundation.org>
Subject: Re: [PATCH 1/2] seccomp: notify user trap about unused filter
Date: Thu, 28 May 2020 06:04:48 +0200 [thread overview]
Message-ID: <CAG48ez3z4TTKHwQmZbeyb+egAdKsFb0kkReSLtJsA+9MP6VUBg@mail.gmail.com> (raw)
In-Reply-To: <20200527111902.163213-1-christian.brauner@ubuntu.com>
On Wed, May 27, 2020 at 1:19 PM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
> We've been making heavy use of the seccomp notifier to intercept and
> handle certain syscalls for containers. This patch allows a syscall
> supervisor listening on a given notifier to be notified when a seccomp
> filter has become unused.
[...]
> To fix this, we introduce a new "live" reference counter that tracks the
> live tasks making use of a given filter and when a notifier is
> registered waiting tasks will be notified that the filter is now empty
> by receiving a (E)POLLHUP event.
> The concept in this patch introduces is the same as for signal_struct,
> i.e. reference counting for life-cycle management is decoupled from
> reference counting live taks using the object.
[...]
> + * @live: tasks that actually use this filter, only to be altered
> + * during fork(), exit()/free_task(), and filter installation
This comment is a bit off. Actually, @live counts the number of tasks
that use the filter directly plus the number of dependent filters that
have non-zero @live.
[...]
> +void seccomp_filter_notify(const struct task_struct *tsk)
> +{
> + struct seccomp_filter *orig = tsk->seccomp.filter;
> +
> + while (orig && refcount_dec_and_test(&orig->live)) {
> + if (waitqueue_active(&orig->wqh))
> + wake_up_poll(&orig->wqh, EPOLLHUP);
> + orig = orig->prev;
> + }
> +}
/me fetches the paint bucket
Maybe name this seccomp_filter_unuse() or
seccomp_filter_unuse_notify() or something like that? The current name
isn't very descriptive.
next prev parent reply other threads:[~2020-05-28 4:05 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 11:19 [PATCH 1/2] seccomp: notify user trap about unused filter Christian Brauner
2020-05-27 11:19 ` [PATCH 2/2] tests: test seccomp filter notifications Christian Brauner
2020-05-27 15:25 ` [PATCH 1/2] seccomp: notify user trap about unused filter Tycho Andersen
2020-05-27 15:35 ` Christian Brauner
2020-05-27 17:37 ` Sargun Dhillon
2020-05-27 19:13 ` Christian Brauner
2020-05-27 21:43 ` Kees Cook
2020-05-27 21:52 ` Tycho Andersen
2020-05-27 22:36 ` Kees Cook
2020-05-27 22:56 ` Tycho Andersen
2020-05-28 1:50 ` Kees Cook
2020-05-27 22:05 ` Christian Brauner
2020-05-27 22:37 ` Kees Cook
2020-05-27 22:45 ` Christian Brauner
2020-05-27 23:16 ` Christian Brauner
2020-05-28 1:59 ` Kees Cook
2020-05-28 4:14 ` Jann Horn
2020-05-28 14:16 ` Christian Brauner
2020-05-28 14:39 ` Christian Brauner
2020-05-28 1:49 ` Kees Cook
2020-05-28 4:04 ` Jann Horn [this message]
2020-05-28 9:57 ` Christian Brauner
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