linux-kernel - Re: Re: [PATCH V3] binder: ipc namespace support for android binder(Internet mail)

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Message-ID: <CAHRSSEynQoksQiQk2x8ZNSnuSM4rQkiD2kk1=AwSQ5o4Lqks3g@mail.gmail.com>
Date:   Fri, 9 Nov 2018 22:38:02 -0800
From:   Todd Kjos <tkjos@...gle.com>
To:     chouryzhou@...cent.com
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>, akpm@...ux-foundation.org,
        dave@...olabs.net,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        LKML <linux-kernel@...r.kernel.org>, chouryzhou@...il.com
Subject: Re: Re: [PATCH V3] binder: ipc namespace support for android
 binder(Internet mail)

On Fri, Nov 9, 2018 at 9:43 PM chouryzhou(周威) <chouryzhou@...cent.com> wrote:
>
> > >
> > > If IPC_NS is disabled, "current-nsporxy->ipc_ns" will also exists,  it 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, everything 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 = 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 -
>