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From:   Todd Kjos <tkjos@google.com>
Date:   Fri, 9 Nov 2018 22:38:02 -0800
Message-ID: <CAHRSSEynQoksQiQk2x8ZNSnuSM4rQkiD2kk1=AwSQ5o4Lqks3g@mail.gmail.com>
Subject: Re: Re: [PATCH V3] binder: ipc namespace support for android
 binder(Internet mail)
To:     chouryzhou@tencent.com
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>, akpm@linux-foundation.org,
        dave@stgolabs.net,
        "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
        LKML <linux-kernel@vger.kernel.org>, chouryzhou@gmail.com
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On Fri, Nov 9, 2018 at 9:43 PM chouryzhou(=E5=91=A8=E5=A8=81) <chouryzhou@t=
encent.com> wrote:
>
> > >
> > > If IPC_NS is disabled, "current-nsporxy->ipc_ns" will also exists,  i=
t will be a static
> > > reference of "init_ipc_ns" (in ipc/msgutil.c, not defined in binder.c=
 by me) with
> > > no namespace-ization. You will get the same one in all processes, eve=
rything is
> > > the same as  without this patch.
> >
> > except, as far as I can tell, binder_init_ns() would never have been
> > called on it so the mutex and list heads are not initialized so its
> > completely broken. Am I missing something? How do those fields get
> > initialized in this case?
>
> > @@ -5832,8 +5888,12 @@ static int __init binder_init(void)
> >                         goto err_init_binder_device_failed;
> >         }
> >
> > -       return ret;
> > +       ret =3D binder_init_ns(&init_ipc_ns);
> > +       if (ret)
> > +               goto err_init_namespace_failed;
> >
> > +       return ret;
>
> They are initialized here.

Ok, This init_ipc_ns is a global declared in msgutil.c if SYSVIPC ||
POSIX_MQUEUE. This seems kinda hacky, but now I finally see why the
dependancy... msgutil.c is the only file we can count on if !IPC_NS &&
(SYSVIPC || POSIX_MQUEUE). There must be a cleaner way to do this, I
really don't like this dependency... wouldn't it be cleaner to do:

#ifndef CONFIG_IPC_NS
static struct ipc_namespace binder_ipc_ns;
#define ipcns  (&binder_ipc_ns)
#else
#define ipcns  (current->nsproxy->ipc_ns)
#endif

(and make the initialization of binder_ipc_ns conditional on IPC_NS)

This gets us the same thing without the incestuous dependency on the
msgutil.c version of init_ipc_ns...and then binder doesn't rely on
SYSVIPC or POSIX_MQUEUE directly.

>
> - choury -
>