From: Tycho Andersen <tycho@tycho.ws>
To: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>,
kernel list <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH 3/3] seccomp: introduce read protection for struct seccomp
Date: Fri, 28 Sep 2018 14:56:52 -0600 [thread overview]
Message-ID: <20180928205652.GC18045@cisco.lan> (raw)
In-Reply-To: <CAG48ez2h51s1VG8hf1ASHHq88r5b+6rS4nSkgvre77jgsJLbhg@mail.gmail.com>
On Fri, Sep 28, 2018 at 10:33:34PM +0200, Jann Horn wrote:
> On Fri, Sep 28, 2018 at 5:47 PM Tycho Andersen <tycho@tycho.ws> wrote:
> > As Jann pointed out, there is a race between SECCOMP_FILTER_FLAG_TSYNC and
> > the ptrace code that can inspect a filter of another process. Let's
> > introduce read locking into the two ptrace accesses so that we don't race.
>
> Hmm. Is that true? The ptrace code uses get_nth_filter(), which holds
> the siglock while grabbing the seccomp filter and bumping its
> refcount. And TSYNC happens from seccomp_set_mode_filter(), which
> takes the siglock. So this looks okay to me?
Oh, yes, you're right. So I guess we should just change the comment to
say we're using siglock to represent the read lock.
Tycho
next prev parent reply other threads:[~2018-09-28 20:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-28 15:46 [PATCH 1/3] seccomp: change return type of seccomp_get_metadata to int Tycho Andersen
2018-09-28 15:46 ` [PATCH 2/3] seccomp: change return type of seccomp_get_filter " Tycho Andersen
2018-09-28 15:46 ` [PATCH 3/3] seccomp: introduce read protection for struct seccomp Tycho Andersen
2018-09-28 20:33 ` Jann Horn
2018-09-28 20:56 ` Tycho Andersen [this message]
2018-09-28 21:10 ` Jann Horn
2018-09-28 21:35 ` Tycho Andersen
2018-09-28 21:54 ` Jann Horn
2018-09-28 22:02 ` Tycho Andersen
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