Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 14 Nov 2019 16:50:52 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Adrian Reber <areber@redhat.com>
Cc:     Christian Brauner <christian.brauner@ubuntu.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Pavel Emelyanov <ovzxemul@gmail.com>,
        Jann Horn <jannh@google.com>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-kernel@vger.kernel.org, Andrei Vagin <avagin@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Radostin Stoyanov <rstoyanov1@gmail.com>
Subject: Re: [PATCH v10 1/2] fork: extend clone3() to support setting a PID
Message-ID: <20191114155052.GA13149@redhat.com>
References: <20191114142707.1608679-1-areber@redhat.com>
MIME-Version: 1.0
In-Reply-To: <20191114142707.1608679-1-areber@redhat.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Content-Type: text/plain; charset=WINDOWS-1252
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 11/14, Adrian Reber wrote:
>
> @@ -2600,6 +2602,15 @@ noinline static int copy_clone_args_from_user(stru=
ct kernel_clone_args *kargs,
>  =09if (err)
>  =09=09return err;
>
> +=09if (unlikely(args.set_tid_size > MAX_PID_NS_LEVEL))
> +=09=09return -EINVAL;

so we need this to because copy_from_user() below writes into the
set_tid[MAX_PID_NS_LEVEL] on the caller's stack, then later alloc_pid()
does another "correct" check... We could simply shift that check here,
but probably this would be less clear, so I won't argue.

> @@ -2617,8 +2628,16 @@ noinline static int copy_clone_args_from_user(stru=
ct kernel_clone_args *kargs,
>  =09=09.stack=09=09=3D args.stack,
>  =09=09.stack_size=09=3D args.stack_size,
>  =09=09.tls=09=09=3D args.tls,
> +=09=09.set_tid_size=09=3D args.set_tid_size,
>  =09};
...
> +=09kargs->set_tid =3D kset_tid;

this looks a bit strange, you could simply do

=09=09.set_tid_size   =3D args.set_tid_size,
=09=09.set_tid=09=3D kset_tid,

but this is really minor.

Looks good to me,

Reviewed-by: Oleg Nesterov <oleg@redhat.com>