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From: Kees Cook <keescook@chromium.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Yongji Xie <xieyongji@bytedance.com>,
	devel@driverdev.osuosl.org, tkjos@android.com, maco@android.com,
	Jason Wang <jasowang@redhat.com>,
	joel@joelfernandes.org, Christoph Hellwig <hch@infradead.org>,
	Hridya Valsaraju <hridya@google.com>,
	arve@android.com, viro@zeniv.linux.org.uk,
	Sargun Dhillon <sargun@sargun.me>,
	linux-fsdevel@vger.kernel.org,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Suren Baghdasaryan <surenb@google.com>
Subject: Re: Re: Re: Re: [PATCH 2/2] binder: Use receive_fd() to receive file from another process
Date: Fri, 2 Apr 2021 02:12:51 -0700	[thread overview]
Message-ID: <202104020210.9A945E5@keescook> (raw)
In-Reply-To: <YGXUNfsExs6tZD0c@kroah.com>

On Thu, Apr 01, 2021 at 04:09:57PM +0200, Greg KH wrote:
> On Thu, Apr 01, 2021 at 08:28:02PM +0800, Yongji Xie wrote:
> > On Thu, Apr 1, 2021 at 7:33 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Thu, Apr 01, 2021 at 07:29:45PM +0800, Yongji Xie wrote:
> > > > On Thu, Apr 1, 2021 at 6:42 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > >
> > > > > On Thu, Apr 01, 2021 at 06:12:51PM +0800, Yongji Xie wrote:
> > > > > > On Thu, Apr 1, 2021 at 5:54 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > > > >
> > > > > > > On Thu, Apr 01, 2021 at 05:09:32PM +0800, Xie Yongji wrote:
> > > > > > > > Use receive_fd() to receive file from another process instead of
> > > > > > > > combination of get_unused_fd_flags() and fd_install(). This simplifies
> > > > > > > > the logic and also makes sure we don't miss any security stuff.
> > > > > > >
> > > > > > > But no logic is simplified here, and nothing is "missed", so I do not
> > > > > > > understand this change at all.
> > > > > > >
> > > > > >
> > > > > > I noticed that we have security_binder_transfer_file() when we
> > > > > > transfer some fds. I'm not sure whether we need something like
> > > > > > security_file_receive() here?
> > > > >
> > > > > Why would you?  And where is "here"?
> > > > >
> > > > > still confused,
> > > > >
> > > >
> > > > I mean do we need to go through the file_receive seccomp notifier when
> > > > we receive fd (use get_unused_fd_flags() + fd_install now) from
> > > > another process in binder_apply_fd_fixups().
> > >
> > > Why?  this is internal things, why does seccomp come into play here?
> > >
> > 
> > We already have security_binder_transfer_file() to control the sender
> > process. So for the receiver process, do we need the seccomp too? Or
> > do I miss something here?
> 
> I do not know, is this something that is a requirement that seccomp
> handle all filesystem handles sent to a process?  I do not know the
> seccomp "guarantee" that well, sorry.

This is an extremely confused thread. seccomp _uses_ the receive_fd()
API. receive_fd() calls the security_file_receive() LSM hook. The
security_binder_*() LSM hooks are different yet.

Please, let's wait for Christian to clarify his idea first.

-- 
Kees Cook

  reply	other threads:[~2021-04-02  9:12 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01  9:09 [PATCH 0/2] Export receive_fd() to modules and do some cleanups Xie Yongji
2021-04-01  9:09 ` [PATCH 1/2] file: Export receive_fd() to modules Xie Yongji
2021-04-01  9:52   ` Greg KH
2021-04-01 10:24     ` Yongji Xie
2021-04-01  9:09 ` [PATCH 2/2] binder: Use receive_fd() to receive file from another process Xie Yongji
2021-04-01  9:54   ` Greg KH
2021-04-01 10:12     ` Yongji Xie
2021-04-01 10:42       ` Greg KH
2021-04-01 11:29         ` Yongji Xie
2021-04-01 11:33           ` Greg KH
2021-04-01 12:28             ` Yongji Xie
2021-04-01 14:09               ` Greg KH
2021-04-02  9:12                 ` Kees Cook [this message]
2021-04-01 10:40     ` Christian Brauner
2021-04-01 11:11       ` Yongji Xie
2021-04-16  5:19       ` Al Viro
2021-04-16  5:55         ` Al Viro
2021-04-16 13:42           ` Christian Brauner
2021-04-16 14:09             ` Al Viro
2021-04-16 15:13               ` Christian Brauner
2021-04-16 15:35                 ` Al Viro
2021-04-16 15:58                   ` Christian Brauner
2021-04-16 16:00                     ` Christian Brauner
2021-04-16 17:00                       ` Al Viro
2021-04-16 17:30                     ` Al Viro
2021-04-17  1:30                       ` Al Viro
2021-04-01  9:53 ` [PATCH 0/2] Export receive_fd() to modules and do some cleanups Greg KH
2021-04-01 10:00   ` Yongji Xie
2021-04-01 10:20 ` Christian Brauner

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