linux-kernel - Re: [RFC 00/12] module: avoid userspace pressure on unwanted allocations

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Date:   Fri, 24 Mar 2023 12:11:07 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, petr.pavlu@...e.com, prarit@...hat.com,
        christophe.leroy@...roup.eu, song@...nel.org, dave@...olabs.net,
        fan.ni@...sung.com, vincent.fu@...sung.com,
        a.manzanares@...sung.com, colin.i.king@...il.com
Subject: Re: [RFC 00/12] module: avoid userspace pressure on unwanted allocations

On Fri, Mar 24, 2023 at 10:54 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> +/*
> + * This clutch ensures we only allow a certain number concurrent threads at a

kludge, not clutch.

And it's much worse than a kludge. It's just wrong and disgusting.

> +               pr_warn_ratelimited("kread_concurrent_max (%u) close to 0 (max_loads: %u), throttling...",
> +                                   atomic_read(&kread_concurrent_max),
> +                                   MAX_KREAD_CONCURRENT);

This is also wrong, since it's not kernel_read_file() that is the
problem, but whatever broken caller.

Yeah, yeah, in practice it's presumably always just finit_module()
doing kernel_read_file_from_fd(), but it's still *completely* wrong to
just say "function X is throttling" when "X" isn't the problem, and
doesn't tell what the _real_ problem is.

I really think this all needs some core fixing at the module layer,
not these kinds of horrific hacks.

          Linus