Date: Tue, 8 Jun 2021 16:19:31 -0700 From: Kees Cook <keescook@...omium.org> To: John Wood <john.wood@....com> Cc: Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Shuah Khan <shuah@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>, Andi Kleen <ak@...ux.intel.com>, valdis.kletnieks@...edu, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Randy Dunlap <rdunlap@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-arch@...r.kernel.org, linux-hardening@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH v8 0/8] Fork brute force attack mitigation 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. It seems like there is a need to track "user" running "prog", and have that be timed out. Are there use-cases here where that wouldn't be sufficient? -Kees -- Kees Cook
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