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Date: Mon, 22 May 2023 13:12:52 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Simon Horman <simon.horman@corigine.com>
Cc: Christian Brauner <brauner@kernel.org>, kernel test robot
 <lkp@intel.com>, Eric Dumazet <edumazet@google.com>, Alexander Mikhalitsyn
 <aleksandr.mikhalitsyn@canonical.com>, davem@davemloft.net,
 oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org,
 netdev@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>, Leon Romanovsky
 <leon@kernel.org>, David Ahern <dsahern@kernel.org>, Arnd Bergmann
 <arnd@arndb.de>, Kees Cook <keescook@chromium.org>, Kuniyuki Iwashima
 <kuniyu@amazon.com>, Lennart Poettering <mzxreary@0pointer.de>, Luca
 Boccassi <bluca@debian.org>, linux-arch@vger.kernel.org
Subject: Re: [PATCH net-next v5 1/3] scm: add SO_PASSPIDFD and SCM_PIDFD
Message-ID: <20230522131252.4f9959d3@kernel.org>
In-Reply-To: <ZGtr1RwK42We5ACI@corigine.com>
References: <20230517113351.308771-2-aleksandr.mikhalitsyn@canonical.com>
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On Mon, 22 May 2023 15:19:17 +0200 Simon Horman wrote:
> > TLI, that AF_UNIX can be a kernel module...
> > I'm really not excited in exposing pidfd_prepare() to non-core kernel
> > code. Would it be possible to please simply refuse SO_PEERPIDFD and
> > SCM_PIDFD if AF_UNIX is compiled as a module? I feel that this must be
> > super rare because it risks breaking even simplistic userspace.  
> 
> It occurs to me that it may be simpler to not allow AF_UNIX to be a module.
> But perhaps that breaks something for someone...

Both of the two options (disable the feature with unix=m, make unix
bool) could lead to breakage, I reckon at least the latter makes
the breakage more obvious? So not allowing AF_UNIX as a module
gets my vote as well.

A mechanism of exporting symbols for core/internal use only would 
find a lot of use in networking :(