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Date:   Tue, 8 Jun 2021 16:38:15 -0700
From:   Andi Kleen <>
To:     Kees Cook <>, John Wood <>
Cc:     Jann Horn <>, Jonathan Corbet <>,
        James Morris <>,
        "Serge E. Hallyn" <>,
        Shuah Khan <>,
        Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,, "H. Peter Anvin" <>,
        Arnd Bergmann <>,,
        Greg Kroah-Hartman <>,
        Randy Dunlap <>,
        Andrew Morton <>,,,,,,,
Subject: Re: [PATCH v8 0/8] Fork brute force attack mitigation

On 6/8/2021 4:19 PM, Kees Cook wrote:
> On Sat, Jun 05, 2021 at 05:03:57PM +0200, John Wood wrote:
>> [...]
>> the kselftest to avoid the detection ;) ). So, in this version, to track
>> all the statistical data (info related with application crashes), the
>> extended attributes feature for the executable files are used. The xattr is
>> also used to mark the executables as "not allowed" when an attack is
>> detected. Then, the execve system call rely on this flag to avoid following
>> executions of this file.
> I have some concerns about this being actually usable and not creating
> DoS situations. For example, let's say an attacker had found a hard-to-hit
> bug in "sudo", and starts brute forcing it. When the brute LSM notices,
> it'll make "sudo" unusable for the entire system, yes?
> And a reboot won't fix it, either, IIUC.
The whole point of the mitigation is to trade potential attacks against DOS.

If you're worried about DOS the whole thing is not for you.


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