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Date:   Thu, 21 Nov 2019 12:27:20 +0100
From:   Christian Brauner <christian.brauner@ubuntu.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc:     Christian Brauner <christian@brauner.io>, adrian@lisas.de,
        akpm@linux-foundation.org, arnd@arndb.de, avagin@gmail.com,
        dhowells@redhat.com, fweimer@redhat.com, jannh@google.com,
        keescook@chromium.org, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-man@vger.kernel.org,
        mingo@elte.hu, oleg@redhat.com, xemul@virtuozzo.com
Subject: Re: [PATCH] clone.2: Mention that CLONE_PARENT is off-limits for
 inits
Message-ID: <20191121112719.lg3qxptnowjkpxlg@wittgenstein>
References: <20191120104504.22411-1-christian@brauner.io>
 <ac6c1644-c6d3-c7eb-48b1-28eb9342a468@gmail.com>
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On Thu, Nov 21, 2019 at 10:53:50AM +0100, Michael Kerrisk (man-pages) wrote:
> Hello Christian,
> 
> On 11/20/19 11:45 AM, Christian Brauner wrote:
> > From: Christian Brauner <christian.brauner@ubuntu.com>
> > 
> > The CLONE_PARENT flag cannot but used by init processes. Let's mention
> > this in the manpages to prevent suprises.
> > 
> > Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> > ---
> >  man2/clone.2 | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/man2/clone.2 b/man2/clone.2
> > index f0f29d6f1..aa98ab79b 100644
> > --- a/man2/clone.2
> > +++ b/man2/clone.2
> > @@ -646,6 +646,13 @@ if
> >  .B CLONE_PARENT
> >  is set, then the parent of the calling process, rather than the
> >  calling process itself, will be signaled.
> > +.IP
> > +The kernel will not allow global init and init processes in pid
> > +namespaces to use the
> > +.B CLONE_PARENT
> > +flag. This is done to prevent the creation of multi-rooted process
> > +trees. It also avoids unreapable zombies in the initial pid
> > +namespace.
> >  .TP
> >  .BR CLONE_PARENT_SETTID " (since Linux 2.5.49)"
> >  Store the child thread ID at the location pointed to by
> 
> Thank. I applied, and then tweaked the text a little,
> and noted the associated EINVAL error. In the end, the
> change is as below.

Thanks!
Christian