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From: jvoisin <julien.voisin@dustri.org>
To: keescook@chromium.org
Cc: ast@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com,
	hpa@zytor.com, jgross@suse.com, jpoimboe@kernel.org,
	leitao@debian.org, linux-hardening@vger.kernel.org,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	nathan@kernel.org, peterz@infradead.org, samitolvanen@google.com,
	tglx@linutronix.de, x86@kernel.org
Subject: Re: [PATCH] x86/alternatives: Make FineIBT mode Kconfig selectable
Date: Mon, 29 Jul 2024 14:35:02 +0200	[thread overview]
Message-ID: <c875722b-0434-41fe-b375-cc685498c444@dustri.org> (raw)
In-Reply-To: <20240501000218.work.998-kees@kernel.org>

> Since FineIBT performs checking at the destination, it is weaker against
> attacks that can construct arbitrary executable memory contents. As such,
> some system builders want to run with FineIBT disabled by default. Allow
> the "cfi=kcfi" boot param mode to be selectable through Kconfig via the
> newly introduced CONFIG_CFI_AUTO_DEFAULT.

I'm confused as why you think that KCFI is stronger/better than FineIBT.
The latter is compatible with execute-only memory, makes use of hardware
support, doesn't need LTO, is faster, … moreover, I don't see why an
attacker able to "construct arbitrary executable memory contents"
wouldn't be able to bypass KCFI as well, since its threat model
(https://github.com/kcfi/docs/blob/master/kCFI_whitepaper.pdf)
explicitly says "We assume an OS that fully implements the W^X policy
[56,58,106] preventing direct code injection in kernel space."

  parent reply	other threads:[~2024-07-29 12:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-01  0:02 Kees Cook
2024-05-01 16:33 ` Nathan Chancellor
2024-05-01 20:13   ` Kees Cook
2024-05-01 20:18 ` Sami Tolvanen
2024-07-29 12:35 ` jvoisin [this message]
2024-07-30  0:41   ` Kees Cook

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