Re: [PATCH v6 01/10] file: Export receive_fd() to modules

From: Christian Brauner <christian.brauner@ubuntu.com>
To: Yongji Xie <xieyongji@bytedance.com>
Cc: "Christoph Hellwig" <hch@infradead.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Jason Wang" <jasowang@redhat.com>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Stefano Garzarella" <sgarzare@redhat.com>,
	"Parav Pandit" <parav@nvidia.com>,
	"Christian Brauner" <christian.brauner@canonical.com>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	viro@zeniv.linux.org.uk, "Jens Axboe" <axboe@kernel.dk>,
	bcrl@kvack.org, "Jonathan Corbet" <corbet@lwn.net>,
	"Mika Penttilä" <mika.penttila@nextfour.com>,
	"Dan Carpenter" <dan.carpenter@oracle.com>,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, kvm@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v6 01/10] file: Export receive_fd() to modules
Date: Wed, 31 Mar 2021 16:07:59 +0200	[thread overview]
Message-ID: <20210331140759.rxfpfcavzus3lomp@wittgenstein> (raw)
In-Reply-To: <CACycT3vm_XvitXV+kXivAhrfwN6U0Nm5kZwcYhY+GrriVAKq8g@mail.gmail.com>

On Wed, Mar 31, 2021 at 09:59:07PM +0800, Yongji Xie wrote:
> On Wed, Mar 31, 2021 at 8:23 PM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
> >
> > On Wed, Mar 31, 2021 at 07:32:33PM +0800, Yongji Xie wrote:
> > > On Wed, Mar 31, 2021 at 5:15 PM Christian Brauner
> > > <christian.brauner@ubuntu.com> wrote:
> > > >
> > > > On Wed, Mar 31, 2021 at 04:05:10PM +0800, Xie Yongji wrote:
> > > > > Export receive_fd() so that some modules can use
> > > > > it to pass file descriptor between processes without
> > > > > missing any security stuffs.
> > > > >
> > > > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > > > ---
> > > >
> > > > Yeah, as I said in the other mail I'd be comfortable with exposing just
> > > > this variant of the helper.
> > >
> > > Thanks, I got it now.
> > >
> > > > Maybe this should be a separate patch bundled together with Christoph's
> > > > patch to split parts of receive_fd() into a separate helper.
> > >
> > > Do we need to add the seccomp notifier into the separate helper? In
> > > our case, the file passed to the separate helper is from another
> > > process.
> >
> > Not sure what you mean. Christoph has proposed
> > https://lore.kernel.org/linux-fsdevel/20210325082209.1067987-2-hch@lst.de
> > I was just saying that if we think this patch is useful we might bundle
> > it together with the
> > EXPORT_SYMBOL(receive_fd)
> > part here, convert all drivers that currently open-code get_unused_fd()
> > + fd_install() to use receive_fd(), and make this a separate patchset.
> >
> 
> Yes, I see. We can split the parts (get_unused_fd() + fd_install()) of
> receive_fd() into a separate helper and convert all drivers to use
> that. What I mean is that I also would like to use
> security_file_receive() in my modules. So I'm not sure if it's ok to
> add security_file_receive() into the separate helper. Or do I need to
> export security_file_receive() separately?

I think I confused you which is my bad. What you do here is - in my
opinion - correct.
I'm just saying that exporting receive_fd() allows further cleanups and
your export here could go on top of Christoph's change in a separate
series.

Christian