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Date:   Sat, 3 Jul 2021 12:59:28 +0200
From:   John Wood <>
To:     Alexander Lobakin <>
Cc:     John Wood <>, Kees Cook <>,
        Jann Horn <>, Jonathan Corbet <>,
        James Morris <>,
        "Serge E. Hallyn" <>,
        Shuah Khan <>,
        Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,, "H. Peter Anvin" <>,
        Arnd Bergmann <>, Andi Kleen <>,,
        Greg Kroah-Hartman <>,
        Randy Dunlap <>,
        Andrew Morton <>,,,,,,,
Subject: Re: [PATCH v8 3/8] security/brute: Detect a brute force attack


On Fri, Jul 02, 2021 at 05:08:09PM +0000, Alexander Lobakin wrote:
> On the other hand, it leaves a potentional window for attackers to
> perform brute force from xattr-incapable filesystems. So at the end
> of the day I think that the current implementation (a strong
> rejection of such filesystems) is way more secure than having
> a fallback I proposed.

I've been thinking more about this: that the Brute LSM depends on xattr
support and I don't like this part. I want that brute force attacks can
be detected and mitigated on every system (with minimal dependencies).
So, now I am working in a solution without this drawback. I have some
ideas but I need to work on it.

> I'm planning to make a patch which will eliminate such weird rootfs
> type selection and just always use more feature-rich tmpfs if it's
> compiled in. So, as an alternative, you could add it to your series
> as a preparatory change and just add a Kconfig dependency on
> without messing with any fallbacks at all.
> What do you think?

Great. But I hope this patch will not be necessary for Brute LSM :)

John Wood

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