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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
Date: Tue, 30 Apr 2024 14:15:53 -0700	[thread overview]
Message-ID: <202404301409.D3BC98D5@keescook> (raw)
In-Reply-To: <202404301037.9E34D4811@keescook>

On Tue, Apr 30, 2024 at 10:48:36AM -0700, Kees Cook wrote:
> 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...

And FINEIBT actually can't be disabled... :|

And as it turns out CFI_CLANG doesn't work at all on v6.9...

[    0.587220] no CFI hash found at: __call_sites+0x339a8/0x34450 ffffffffac20cef8 00 00 00 00 00
[    0.588226] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:1182 __apply_fineibt+0x7a9/0x820
...
[    0.619220] SMP alternatives: Something went horribly wrong trying to rewrite the CFI implementation.
*hang*



-- 
Kees Cook

WARNING: multiple messages have this Message-ID (diff)
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
Date: Tue, 30 Apr 2024 14:15:53 -0700	[thread overview]
Message-ID: <202404301409.D3BC98D5@keescook> (raw)
In-Reply-To: <202404301037.9E34D4811@keescook>

On Tue, Apr 30, 2024 at 10:48:36AM -0700, Kees Cook wrote:
> 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...

And FINEIBT actually can't be disabled... :|

And as it turns out CFI_CLANG doesn't work at all on v6.9...

[    0.587220] no CFI hash found at: __call_sites+0x339a8/0x34450 ffffffffac20cef8 00 00 00 00 00
[    0.588226] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:1182 __apply_fineibt+0x7a9/0x820
...
[    0.619220] SMP alternatives: Something went horribly wrong trying to rewrite the CFI implementation.
*hang*



-- 
Kees Cook

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2024-04-30 21:15 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-26 22:29 [PATCH] hardening: Refresh KCFI options, add some more Kees Cook
2024-04-26 22:29 ` Kees Cook
2024-04-29 22:16 ` Nathan Chancellor
2024-04-29 22:16   ` Nathan Chancellor
2024-04-30  5:35   ` Kees Cook
2024-04-30  5:35     ` Kees Cook
2024-04-30 15:12     ` Nathan Chancellor
2024-04-30 15:12       ` Nathan Chancellor
2024-04-30  9:21 ` Peter Zijlstra
2024-04-30  9:21   ` Peter Zijlstra
2024-04-30 17:48   ` Kees Cook
2024-04-30 17:48     ` Kees Cook
2024-04-30 21:15     ` Kees Cook [this message]
2024-04-30 21:15       ` Kees Cook
2024-04-30 21:25       ` Kees Cook
2024-04-30 21:25         ` Kees Cook
2024-05-01 11:06     ` Peter Zijlstra
2024-05-01 11:06       ` Peter Zijlstra
2024-05-01 19:27       ` Kees Cook
2024-05-01 19:27         ` Kees Cook

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