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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 9 Mar 2018 11:12:17 -0800
Message-ID: <CA+55aFyN8JDh76bm1VinBvrgMH5jNL6RbuFAkrH8vuYU1s9GDQ@mail.gmail.com>
Subject: Re: [PATCH net-next] modules: allow modprobe load regular elf binaries
To:     David Miller <davem@davemloft.net>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        Alexei Starovoitov <ast@fb.com>,
        Kees Cook <keescook@chromium.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Djalal Harouni <tixxdz@gmail.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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On Fri, Mar 9, 2018 at 10:57 AM, David Miller <davem@davemloft.net> wrote:
>
> Once the helper UMH is invoked, it runs asynchronously taking eBPF
> translation requests.

How?

Really. See my comment about mutual exclusion. The current patch is
*broken* because it doesn't handle it. Really.

Think of it this way - you may have now started *five* of those things
concurrently by mistake.

The actual module loading case never does that, because the actual
module loading case has per-module serialization that got
short-circuited.

How are you going to handle five processes doing the same setup concurrently?

                  Linus