From: Nick Desaulniers <ndesaulniers@google.com>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Nathan Chancellor <nathan@kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Christoph Hellwig <hch@infradead.org>, bpf <bpf@vger.kernel.org>,
linux-hardening@vger.kernel.org,
linux-arch <linux-arch@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
PCI <linux-pci@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 02/17] cfi: add __cficanonical
Date: Thu, 18 Mar 2021 10:49:50 -0700 [thread overview]
Message-ID: <CAKwvOd=CfNmVT0RNsXw=vhTee40xpA-LjmyfagAQesS6VdAkXQ@mail.gmail.com> (raw)
In-Reply-To: <20210318171111.706303-3-samitolvanen@google.com>
On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> With CONFIG_CFI_CLANG, the compiler replaces a function address taken
> in C code with the address of a local jump table entry, which passes
> runtime indirect call checks. However, the compiler won't replace
> addresses taken in assembly code, which will result in a CFI failure
> if we later jump to such an address in instrumented C code. The code
> generated for the non-canonical jump table looks this:
>
> <noncanonical.cfi_jt>: /* In C, &noncanonical points here */
> jmp noncanonical
> ...
> <noncanonical>: /* function body */
> ...
>
> This change adds the __cficanonical attribute, which tells the
> compiler to use a canonical jump table for the function instead. This
> means the compiler will rename the actual function to <function>.cfi
> and points the original symbol to the jump table entry instead:
>
> <canonical>: /* jump table entry */
> jmp canonical.cfi
> ...
> <canonical.cfi>: /* function body */
> ...
>
> As a result, the address taken in assembly, or other non-instrumented
> code always points to the jump table and therefore, can be used for
> indirect calls in instrumented code without tripping CFI checks.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci.h
Irrelevant to this series, but I checked when the FN attr was first
available in clang; clang-10. (That's the minimum supported version of
clang for the kernel, and this series depends on LTO which depends on
clang-12, so no additional guards are necessary).
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> include/linux/compiler-clang.h | 1 +
> include/linux/compiler_types.h | 4 ++++
> include/linux/init.h | 4 ++--
> include/linux/pci.h | 4 ++--
> 4 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 6de9d0c9377e..adbe76b203e2 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -63,3 +63,4 @@
> #endif
>
> #define __nocfi __attribute__((__no_sanitize__("cfi")))
> +#define __cficanonical __attribute__((__cfi_canonical_jump_table__))
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index 796935a37e37..d29bda7f6ebd 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -246,6 +246,10 @@ struct ftrace_likely_data {
> # define __nocfi
> #endif
>
> +#ifndef __cficanonical
> +# define __cficanonical
> +#endif
> +
> #ifndef asm_volatile_goto
> #define asm_volatile_goto(x...) asm goto(x)
> #endif
> diff --git a/include/linux/init.h b/include/linux/init.h
> index b3ea15348fbd..045ad1650ed1 100644
> --- a/include/linux/init.h
> +++ b/include/linux/init.h
> @@ -220,8 +220,8 @@ extern bool initcall_debug;
> __initcall_name(initstub, __iid, id)
>
> #define __define_initcall_stub(__stub, fn) \
> - int __init __stub(void); \
> - int __init __stub(void) \
> + int __init __cficanonical __stub(void); \
> + int __init __cficanonical __stub(void) \
> { \
> return fn(); \
> } \
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 86c799c97b77..39684b72db91 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1944,8 +1944,8 @@ enum pci_fixup_pass {
> #ifdef CONFIG_LTO_CLANG
> #define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \
> class_shift, hook, stub) \
> - void stub(struct pci_dev *dev); \
> - void stub(struct pci_dev *dev) \
> + void __cficanonical stub(struct pci_dev *dev); \
> + void __cficanonical stub(struct pci_dev *dev) \
> { \
> hook(dev); \
> } \
> --
> 2.31.0.291.g576ba9dcdaf-goog
>
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2021-03-18 17:51 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 17:10 [PATCH v2 00/17] Add support for Clang CFI Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 01/17] add " Sami Tolvanen
2021-03-18 22:29 ` Peter Zijlstra
2021-03-18 23:48 ` Sami Tolvanen
2021-03-19 12:26 ` Peter Zijlstra
2021-03-19 13:52 ` Paul E. McKenney
2021-03-19 16:17 ` Sami Tolvanen
2021-03-19 17:03 ` Paul E. McKenney
2021-03-18 17:10 ` [PATCH v2 02/17] cfi: add __cficanonical Sami Tolvanen
2021-03-18 17:49 ` Nick Desaulniers [this message]
2021-03-18 17:10 ` [PATCH v2 03/17] mm: add generic __va_function and __pa_function macros Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 04/17] module: ensure __cfi_check alignment Sami Tolvanen
2021-03-18 19:27 ` Nick Desaulniers
2021-03-18 21:43 ` Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 05/17] workqueue: use WARN_ON_FUNCTION_MISMATCH Sami Tolvanen
2021-03-18 18:50 ` Nick Desaulniers
2021-03-18 21:38 ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 06/17] kthread: " Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 07/17] kallsyms: strip ThinLTO hashes from static functions Sami Tolvanen
2021-03-18 19:00 ` Nick Desaulniers
2021-03-18 21:41 ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 08/17] bpf: disable CFI in dispatcher functions Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 09/17] lib/list_sort: fix function type mismatches Sami Tolvanen
2021-03-18 18:31 ` Nick Desaulniers
2021-03-18 21:31 ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 10/17] lkdtm: use __va_function Sami Tolvanen
2021-03-18 18:43 ` Nick Desaulniers
2021-03-18 18:45 ` Nick Desaulniers
2021-03-18 17:11 ` [PATCH v2 11/17] psci: use __pa_function for cpu_resume Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 12/17] arm64: implement __va_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 13/17] arm64: use __pa_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 14/17] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 15/17] arm64: add __nocfi to __apply_alternatives Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 16/17] KVM: arm64: Disable CFI for nVHE Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 17/17] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
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