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From: Sami Tolvanen <samitolvanen@google.com>
To: Tom Stellard <tstellar@redhat.com>
Cc: X86 ML <x86@kernel.org>, Kees Cook <keescook@chromium.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	linux-hardening@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v2 00/14] x86: Add support for Clang CFI
Date: Tue, 24 Aug 2021 10:30:55 -0700	[thread overview]
Message-ID: <CABCJKudiTVXOdzxzY1OxF4MMtwNt4XZ_-JJ70dM9H8AEHJmLNw@mail.gmail.com> (raw)
In-Reply-To: <9349a92d-f2a7-9ee4-64db-98d30eadc505@redhat.com>

On Tue, Aug 24, 2021 at 10:26 AM Tom Stellard <tstellar@redhat.com> wrote:
>
> On 8/23/21 10:20 AM, Sami Tolvanen wrote:
> > On Mon, Aug 23, 2021 at 10:16 AM Tom Stellard <tstellar@redhat.com> wrote:
> >>
> >> On 8/23/21 10:13 AM, 'Sami Tolvanen' via Clang Built Linux wrote:
> >>> This series adds support for Clang's Control-Flow Integrity (CFI)
> >>> checking to x86_64. With CFI, the compiler injects a runtime
> >>> check before each indirect function call to ensure the target is
> >>> a valid function with the correct static type. This restricts
> >>> possible call targets and makes it more difficult for an attacker
> >>> to exploit bugs that allow the modification of stored function
> >>> pointers. For more details, see:
> >>>
> >>>     https://clang.llvm.org/docs/ControlFlowIntegrity.html
> >>>
> >>> Version 2 depends on Clang >=14, where we fixed the issue with
> >>> referencing static functions from inline assembly. Based on the
> >>> feedback for v1, this version also changes the declaration of
> >>> functions that are not callable from C to use an opaque type,
> >>> which stops the compiler from replacing references to them. This
> >>> avoids the need to sprinkle function_nocfi() macros in the kernel
> >>> code.
> >>
> >> How invasive are the changes in clang 14 necessary to make CFI work?
> >> Would it be possible to backport them to LLVM 13?
> >
> > I'm not sure what the LLVM backport policy is, but this specific fix
> > was quite simple:
> >
> > https://reviews.llvm.org/rG7ce1c4da7726
> >
>
> That looks like something we could backport, I filed a bug to track
> the backport: https://bugs.llvm.org/show_bug.cgi?id=51588.

Great, thanks!

> Do you have any concerns about backporting it or do you think it's pretty
> safe?

No concerns, it should be safe to backport.

Sami

  reply	other threads:[~2021-08-24 17:56 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-23 17:13 Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 01/14] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 02/14] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 03/14] linkage: Add DECLARE_ASM_FUNC_SYMBOL Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 04/14] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 05/14] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 06/14] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 07/14] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-08-26 16:54   ` Andy Lutomirski
2021-08-26 22:11     ` Sami Tolvanen
2021-08-26 23:23       ` Andy Lutomirski
2021-08-26 23:45         ` Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 08/14] x86/extable: Do not mark exception callback as CFI Sami Tolvanen
2021-08-26 16:56   ` Andy Lutomirski
2021-08-30 19:57     ` Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 09/14] x86/purgatory: Disable CFI Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 10/14] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 11/14] x86, module: " Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 12/14] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 13/14] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-08-23 17:13 ` [PATCH v2 14/14] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
2021-08-23 17:16 ` [PATCH v2 00/14] x86: Add support for Clang CFI Tom Stellard
2021-08-23 17:20   ` Sami Tolvanen
2021-08-24 17:26     ` Tom Stellard
2021-08-24 17:30       ` Sami Tolvanen [this message]
2021-08-24 19:46 ` Peter Zijlstra
2021-08-25 15:49   ` Sami Tolvanen
2021-08-26 11:43     ` Peter Zijlstra
2021-08-26 21:52       ` Sami Tolvanen

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