linux-hardening - Re: [RFC PATCH 3/7] kcfi: Add core Kernel Control Flow Integrity infrastructure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250904071601.GY4067720@noisy.programming.kicks-ass.net>
Date: Thu, 4 Sep 2025 09:16:01 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Kees Cook <kees@...nel.org>
Cc: Qing Zhao <qing.zhao@...cle.com>,
	"gcc-patches@....gnu.org" <gcc-patches@....gnu.org>,
	Joseph Myers <josmyers@...hat.com>,
	Richard Biener <rguenther@...e.de>, Jan Hubicka <hubicka@....cz>,
	Richard Earnshaw <richard.earnshaw@....com>,
	Richard Sandiford <richard.sandiford@....com>,
	Marcus Shawcroft <marcus.shawcroft@....com>,
	Kyrylo Tkachov <kyrylo.tkachov@....com>,
	Kito Cheng <kito.cheng@...il.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Andrew Waterman <andrew@...ive.com>,
	Jim Wilson <jim.wilson.gcc@...il.com>,
	Dan Li <ashimida.1990@...il.com>,
	"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: Re: [RFC PATCH 3/7] kcfi: Add core Kernel Control Flow Integrity
 infrastructure

On Wed, Sep 03, 2025 at 09:24:22PM -0700, Kees Cook wrote:

> > If the hacker knows these, it should be quite easy for them to come up with a
> > matched typeid, is it? 
> 
> The hashes aren't considered secret -- they need to be known/match between
> compilation units, and even across languages (Rust). The KCFI mitigation
> is fundamentally an "exploit surface reduction" measure in the sense
> that it limits an attacker's set of callable functions to only matching
> typeids (instead of all functions or all executable memory). I discuss
> this a big more here:
> https://gcc.gnu.org/pipermail/gcc-patches/2025-August/693059.html

Also note that the kernel with re-hash all the values at boot time once
more -- further increasing the difficulty of an attack.