netdev - Re: [PATCH v6 01/10] file: Export receive

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Date:   Wed, 31 Mar 2021 16:07:59 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Yongji Xie <xieyongji@...edance.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        Christian Brauner <christian.brauner@...onical.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, viro@...iv.linux.org.uk,
        Jens Axboe <axboe@...nel.dk>, bcrl@...ck.org,
        Jonathan Corbet <corbet@....net>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 01/10] file: Export receive_fd() to modules

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@...ntu.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@...ntu.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@...edance.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