From: Kees Cook <keescook@chromium.org>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
Tycho Andersen <tycho@tycho.ws>,
Matt Denton <mpdenton@google.com>,
Sargun Dhillon <sargun@sargun.me>, Jann Horn <jannh@google.com>,
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 v2 1/2] seccomp: notify user trap about unused filter
Date: Fri, 29 May 2020 01:06:59 -0700 [thread overview]
Message-ID: <202005290102.3BB21C875@keescook> (raw)
In-Reply-To: <20200529075641.eoogczu6t5gmv3e3@wittgenstein>
On Fri, May 29, 2020 at 09:56:41AM +0200, Christian Brauner wrote:
> On Thu, May 28, 2020 at 04:11:00PM -0700, Kees Cook wrote:
> > void seccomp_filter_release(const struct task_struct *tsk)
> > {
> > struct seccomp_filter *orig = READ_ONCE(tsk->seccomp.filter);
> >
> > smp_store_release(&tsk->seccomp.filter, NULL);
>
> I need to go through the memory ordering requirements before I can say
> yay or nay confidently to this. :)
>
> > __seccomp_filter_release(orig);
> > }
The only caller will be release_task() after dethread, so honestly this
was just me being paranoid. I don't think it actually needs the
READ_ONCE() nor the store_release. I think I wrote all that before I'd
convinced myself it was safe to remove a filter then. But I'm still
suspicious given the various ways release_task() gets called... I just
know that if mode 2 is set and filter == NULL, seccomp will fail closed,
so I went the paranoid route. :)
--
Kees Cook
next prev parent reply other threads:[~2020-05-29 8:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-28 15:14 [PATCH v2 1/2] seccomp: notify user trap about unused filter Christian Brauner
2020-05-28 15:14 ` [PATCH v2 2/2] tests: test seccomp filter notifications Christian Brauner
2020-05-29 5:41 ` Kees Cook
2020-05-29 8:00 ` Christian Brauner
2020-05-28 23:11 ` [PATCH v2 1/2] seccomp: notify user trap about unused filter Kees Cook
2020-05-28 23:32 ` Jann Horn
2020-05-29 5:36 ` Kees Cook
2020-05-29 7:51 ` Christian Brauner
2020-05-29 7:56 ` Kees Cook
2020-05-29 8:00 ` Christian Brauner
2020-05-29 8:50 ` Christian Brauner
2020-05-29 7:47 ` Christian Brauner
2020-05-29 8:02 ` Kees Cook
2020-05-29 7:56 ` Christian Brauner
2020-05-29 8:06 ` Kees Cook [this message]
2020-05-29 8:37 ` 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=202005290102.3BB21C875@keescook \
--to=keescook@chromium.org \
--cc=christian.brauner@ubuntu.com \
--cc=containers@lists.linux-foundation.org \
--cc=cyphar@cyphar.com \
--cc=jannh@google.com \
--cc=jeffv@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mpdenton@google.com \
--cc=palmer@google.com \
--cc=rsesek@google.com \
--cc=sargun@sargun.me \
--cc=tycho@tycho.ws \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox