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Date: Tue, 30 Apr 2024 10:48:36 -0700
From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	linux-hardening@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] hardening: Refresh KCFI options, add some more
Message-ID: <202404301037.9E34D4811@keescook>
References: <20240426222940.work.884-kees@kernel.org>
 <20240430092140.GE40213@noisy.programming.kicks-ass.net>
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On Tue, Apr 30, 2024 at 11:21:40AM +0200, Peter Zijlstra wrote:
> On Fri, Apr 26, 2024 at 03:29:44PM -0700, Kees Cook wrote:
> 
> > - CONFIG_CFI_CLANG=y for x86 and arm64. (And disable FINEIBT since
> >   it isn't as secure as straight KCFI.)
> 
> Oi ?

Same objection I always had[1]: moving the check into the destination
means attacks with control over executable memory contents can just omit
the check.

But now that I went to go look I see 0c3e806ec0f9 ("x86/cfi: Add boot
time hash randomization") is only enabled under FINEIBT... seems better
if that were always enabled...

-Kees

[1] https://lore.kernel.org/all/202210181020.79AF7F7@keescook/


-- 
Kees Cook