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

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Date:   Wed, 31 Mar 2021 12:26:24 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     Xie Yongji <xieyongji@...edance.com>, hch@...radead.org,
        mst@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        sgarzare@...hat.com, parav@...dia.com,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.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 11:15:45AM +0200, Christian Brauner 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.
> Maybe this should be a separate patch bundled together with Christoph's
> patch to split parts of receive_fd() into a separate helper.
> This would also allow us to simplify a few other codepaths in drivers as
> well btw. I just took a hasty stab at two of them:
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index c119736ca56a..3c716bf6d84b 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -3728,8 +3728,9 @@ static int binder_apply_fd_fixups(struct binder_proc *proc,
>         int ret = 0;
> 
>         list_for_each_entry(fixup, &t->fd_fixups, fixup_entry) {
> -               int fd = get_unused_fd_flags(O_CLOEXEC);
> +               int fd = receive_fd(fixup->file, O_CLOEXEC);
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Assignment duplicated on the next line.

> 
> +               fd = receive_fd(fixup->file, O_CLOEXEC);
>                 if (fd < 0) {
>                         binder_debug(BINDER_DEBUG_TRANSACTION,
>                                      "failed fd fixup txn %d fd %d\n",

regards,
dan carpenter