From: Tom Stellard <tstellar@redhat.com>
To: Sami Tolvanen <samitolvanen@google.com>, x86@kernel.org
Cc: 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, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com
Subject: Re: [PATCH v2 00/14] x86: Add support for Clang CFI
Date: Mon, 23 Aug 2021 10:16:09 -0700 [thread overview]
Message-ID: <1706ee8e-c21c-f867-c0be-24814a92b853@redhat.com> (raw)
In-Reply-To: <20210823171318.2801096-1-samitolvanen@google.com>
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?
-Tom
>
> The first two patches contain objtool support for CFI, the
> remaining patches change function declarations to use opaque
> types, fix type mismatch issues that confuse the compiler, and
> disable CFI where it can't be used.
>
> You can also pull this series from
>
> https://github.com/samitolvanen/linux.git x86-cfi-v2
>
> ---
> Changes in v2:
> - Dropped the first objtool patch as the warnings were fixed in
> separate patches.
>
> - Changed fix_cfi_relocs() in objtool to not rely on jump table
> symbols, and to return an error if it can't find a relocation.
>
> - Fixed a build issue with ASM_STACK_FRAME_NON_STANDARD().
>
> - Dropped workarounds for inline assembly references to
> address-taken static functions with CFI as this was fixed in
> the compiler.
>
> - Changed the C declarations of non-callable functions to use
> opaque types and dropped the function_nocfi() patches.
>
> - Changed ARCH_SUPPORTS_CFI_CLANG to depend on Clang >=14 for
> the compiler fixes.
>
> Kees Cook (2):
> x86/extable: Do not mark exception callback as CFI
> x86, relocs: Ignore __typeid__ relocations
>
> Sami Tolvanen (12):
> objtool: Add CONFIG_CFI_CLANG support
> objtool: Add ASM_STACK_FRAME_NON_STANDARD
> linkage: Add DECLARE_ASM_FUNC_SYMBOL
> ftrace: Use an opaque type for functions not callable from C
> lkdtm: Disable UNSET_SMEP with CFI
> lkdtm: Use an opaque type for lkdtm_rodata_do_nothing
> x86: Use an opaque type for functions not callable from C
> x86/purgatory: Disable CFI
> x86, module: Ignore __typeid__ relocations
> x86, cpu: Use LTO for cpu.c with CFI
> x86, kprobes: Fix optprobe_template_func type mismatch
> x86, build: Allow CONFIG_CFI_CLANG to be selected
>
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/ftrace.h | 2 +-
> arch/x86/include/asm/idtentry.h | 10 +++---
> arch/x86/include/asm/page_64.h | 7 ++--
> arch/x86/include/asm/paravirt_types.h | 3 +-
> arch/x86/include/asm/processor.h | 2 +-
> arch/x86/include/asm/proto.h | 25 ++++++-------
> arch/x86/include/asm/uaccess_64.h | 9 ++---
> arch/x86/kernel/alternative.c | 2 +-
> arch/x86/kernel/ftrace.c | 2 +-
> arch/x86/kernel/kprobes/opt.c | 4 +--
> arch/x86/kernel/module.c | 4 +++
> arch/x86/kernel/paravirt.c | 4 +--
> arch/x86/kvm/emulate.c | 4 +--
> arch/x86/kvm/kvm_emulate.h | 9 ++---
> arch/x86/mm/extable.c | 1 +
> arch/x86/power/Makefile | 2 ++
> arch/x86/purgatory/Makefile | 2 +-
> arch/x86/tools/relocs.c | 7 ++++
> arch/x86/xen/enlighten_pv.c | 6 ++--
> arch/x86/xen/xen-ops.h | 10 +++---
> drivers/misc/lkdtm/bugs.c | 2 +-
> drivers/misc/lkdtm/lkdtm.h | 2 +-
> drivers/misc/lkdtm/perms.c | 2 +-
> drivers/misc/lkdtm/rodata.c | 2 +-
> include/linux/ftrace.h | 7 ++--
> include/linux/linkage.h | 13 +++++++
> include/linux/objtool.h | 6 ++++
> tools/include/linux/objtool.h | 6 ++++
> tools/objtool/arch/x86/decode.c | 16 +++++++++
> tools/objtool/elf.c | 51 +++++++++++++++++++++++++++
> tools/objtool/include/objtool/arch.h | 3 ++
> tools/objtool/include/objtool/elf.h | 2 +-
> 33 files changed, 166 insertions(+), 62 deletions(-)
>
>
> base-commit: d5ae8d7f85b7f6f6e60f1af8ff4be52b0926fde1
>
next prev parent reply other threads:[~2021-08-23 17:16 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 17:13 [PATCH v2 00/14] x86: Add support for Clang CFI 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 ` Tom Stellard [this message]
2021-08-23 17:20 ` [PATCH v2 00/14] x86: Add support for Clang CFI Sami Tolvanen
2021-08-24 17:26 ` Tom Stellard
2021-08-24 17:30 ` Sami Tolvanen
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1706ee8e-c21c-f867-c0be-24814a92b853@redhat.com \
--to=tstellar@redhat.com \
--cc=clang-built-linux@googlegroups.com \
--cc=jpoimboe@redhat.com \
--cc=keescook@chromium.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=samitolvanen@google.com \
--cc=sedat.dilek@gmail.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).