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Date:   Wed, 27 Jun 2018 11:32:09 -0500
From:   "Serge E. Hallyn" <serge@hallyn.com>
To:     Christian Brauner <christian.brauner@canonical.com>
Cc:     Jann Horn <jannh@google.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        kernel list <linux-kernel@vger.kernel.org>,
        security@kernel.org, Andy Lutomirski <luto@amacapital.net>,
        Kees Cook <keescook@chromium.org>,
        "Serge E. Hallyn" <serge@hallyn.com>
Subject: Re: [PATCH] userns: move user access out of the mutex
Message-ID: <20180627163209.GA23160@mail.hallyn.com>
References: <20180625163419.216578-1-jannh@google.com>
 <20180626130757.GA10042@gmail.com>
 <CAG48ez2WwQVWtfh7sQCqn1E52V7V4_LxZaU+kV_r-YGOzNAsXg@mail.gmail.com>
 <20180627142315.GC31443@gmail.com>
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Quoting Christian Brauner (christian.brauner@canonical.com):
> On Tue, Jun 26, 2018 at 04:06:45PM +0200, Jann Horn wrote:
> > On Tue, Jun 26, 2018 at 3:08 PM Christian Brauner
> > <christian.brauner@canonical.com> wrote:
> > >
> > > On Mon, Jun 25, 2018 at 06:34:19PM +0200, Jann Horn wrote:
> > > > The old code would hold the userns_state_mutex indefinitely if
> > > > memdup_user_nul stalled due to e.g. a userfault region. Prevent that by
> > > > moving the memdup_user_nul in front of the mutex_lock().
> > > >
> > > > Note: This changes the error precedence of invalid buf/count/*ppos vs
> > > > map already written / capabilities missing.
> > > >
> > > > Fixes: 22d917d80e84 ("userns: Rework the user_namespace adding uid/gid...")
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Jann Horn <jannh@google.com>
> 
> Acked-by: Christian Brauner <christian@brauner.io>

Acked-by: Serge Hallyn <serge@hallyn.com>

thanks.

-serge