From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: linux-kernel@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>, Peter Zijlstra <peterz@infradead.org>, x86@kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Joao Moreira <joao@overdrivepizza.com>, Sedat Dilek <sedat.dilek@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev Subject: Re: [RFC PATCH v2 07/21] cfi: Add type helper macros Date: Mon, 16 May 2022 09:04:44 -0700 [thread overview] Message-ID: <CABCJKudrY2b4ZXUaXOmKEB-LG192u2PSfsT-=Vc1bcg3QwY6aw@mail.gmail.com> (raw) In-Reply-To: <202205141447.E3B5A29@keescook> On Sat, May 14, 2022 at 2:49 PM Kees Cook <keescook@chromium.org> wrote: > > On Fri, May 13, 2022 at 01:21:45PM -0700, Sami Tolvanen wrote: > > With CONFIG_CFI_CLANG, assembly functions called indirectly > > from C code must be annotated with type identifiers to pass CFI > > checking. The compiler emits a __kcfi_typeid_<function> symbol for > > each address-taken function declaration in C, which contains the > > expected type identifier. Add typed versions of SYM_FUNC_START and > > SYM_FUNC_START_ALIAS, which emit the type identifier before the > > function. > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > And the reason to not make this change universally (i.e. directly in > SYM_FUNC_START) is to minimize how many of these symbol annotations get > emitted? (And to more directly indicate which asm is called indirectly?) The reason not to add this to SYM_FUNC_START is that the compiler doesn't emit the type symbols for all functions. It currently emits them for all address-taken function declarations in each translation unit. We could potentially further limit this by emitting them only for function declarations with a specific attribute, for example, but that's something we can optimize later. > What happens if an asm function is called indirectly and it doesn't have > this annotation? It will fail the CFI check. > (Is this case detectable at compile-time?) It's not. I'll update the commit message in the next version to clarify these points. Sami
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com> To: Kees Cook <keescook@chromium.org> Cc: linux-kernel@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>, Peter Zijlstra <peterz@infradead.org>, x86@kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Joao Moreira <joao@overdrivepizza.com>, Sedat Dilek <sedat.dilek@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev Subject: Re: [RFC PATCH v2 07/21] cfi: Add type helper macros Date: Mon, 16 May 2022 09:04:44 -0700 [thread overview] Message-ID: <CABCJKudrY2b4ZXUaXOmKEB-LG192u2PSfsT-=Vc1bcg3QwY6aw@mail.gmail.com> (raw) In-Reply-To: <202205141447.E3B5A29@keescook> On Sat, May 14, 2022 at 2:49 PM Kees Cook <keescook@chromium.org> wrote: > > On Fri, May 13, 2022 at 01:21:45PM -0700, Sami Tolvanen wrote: > > With CONFIG_CFI_CLANG, assembly functions called indirectly > > from C code must be annotated with type identifiers to pass CFI > > checking. The compiler emits a __kcfi_typeid_<function> symbol for > > each address-taken function declaration in C, which contains the > > expected type identifier. Add typed versions of SYM_FUNC_START and > > SYM_FUNC_START_ALIAS, which emit the type identifier before the > > function. > > > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > And the reason to not make this change universally (i.e. directly in > SYM_FUNC_START) is to minimize how many of these symbol annotations get > emitted? (And to more directly indicate which asm is called indirectly?) The reason not to add this to SYM_FUNC_START is that the compiler doesn't emit the type symbols for all functions. It currently emits them for all address-taken function declarations in each translation unit. We could potentially further limit this by emitting them only for function declarations with a specific attribute, for example, but that's something we can optimize later. > What happens if an asm function is called indirectly and it doesn't have > this annotation? It will fail the CFI check. > (Is this case detectable at compile-time?) It's not. I'll update the commit message in the next version to clarify these points. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-05-16 16:05 UTC|newest] Thread overview: 174+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-13 20:21 [RFC PATCH v2 00/21] KCFI support Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 01/21] efi/libstub: Filter out CC_FLAGS_CFI Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:42 ` Kees Cook 2022-05-14 21:42 ` Kees Cook 2022-05-16 15:44 ` Sami Tolvanen 2022-05-16 15:44 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 02/21] arm64/vdso: " Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:42 ` Kees Cook 2022-05-14 21:42 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 03/21] kallsyms: Ignore __kcfi_typeid_ Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:43 ` Kees Cook 2022-05-14 21:43 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 04/21] cfi: Remove CONFIG_CFI_CLANG_SHADOW Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:43 ` Kees Cook 2022-05-14 21:43 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 05/21] cfi: Drop __CFI_ADDRESSABLE Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:44 ` Kees Cook 2022-05-14 21:44 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 06/21] cfi: Switch to -fsanitize=kcfi Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:46 ` Kees Cook 2022-05-14 21:46 ` Kees Cook 2022-05-15 3:41 ` Kees Cook 2022-05-15 3:41 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 07/21] cfi: Add type helper macros Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:49 ` Kees Cook 2022-05-14 21:49 ` Kees Cook 2022-05-16 12:28 ` Rasmus Villemoes 2022-05-16 12:28 ` Rasmus Villemoes 2022-05-16 16:23 ` Sami Tolvanen 2022-05-16 16:23 ` Sami Tolvanen 2022-05-16 16:04 ` Sami Tolvanen [this message] 2022-05-16 16:04 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 08/21] psci: Fix the function type for psci_initcall_t Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:50 ` Kees Cook 2022-05-14 21:50 ` Kees Cook 2022-05-16 15:44 ` Sami Tolvanen 2022-05-16 15:44 ` Sami Tolvanen 2022-05-17 8:47 ` Mark Rutland 2022-05-17 8:47 ` Mark Rutland 2022-05-13 20:21 ` [RFC PATCH v2 09/21] arm64: Add types to indirect called assembly functions Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:50 ` Kees Cook 2022-05-14 21:50 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 10/21] arm64: Add CFI error handling Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:51 ` Kees Cook 2022-05-14 21:51 ` Kees Cook 2022-05-16 16:24 ` Sami Tolvanen 2022-05-16 16:24 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 11/21] arm64: Drop unneeded __nocfi attributes Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:54 ` Kees Cook 2022-05-14 21:54 ` Kees Cook 2022-05-16 16:28 ` Sami Tolvanen 2022-05-16 16:28 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 12/21] treewide: Drop function_nocfi Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:54 ` Kees Cook 2022-05-14 21:54 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 13/21] treewide: Drop WARN_ON_FUNCTION_MISMATCH Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:54 ` Kees Cook 2022-05-14 21:54 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 14/21] treewide: Drop __cficanonical Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:56 ` Kees Cook 2022-05-14 21:56 ` Kees Cook 2022-05-16 16:32 ` Sami Tolvanen 2022-05-16 16:32 ` Sami Tolvanen 2022-05-13 20:21 ` [RFC PATCH v2 15/21] objtool: Don't warn about __cfi_ preambles falling through Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:56 ` Kees Cook 2022-05-14 21:56 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 16/21] x86/tools/relocs: Ignore __kcfi_typeid_ relocations Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:57 ` Kees Cook 2022-05-14 21:57 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 17/21] x86: Add types to indirectly called assembly functions Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:58 ` Kees Cook 2022-05-14 21:58 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 18/21] x86/purgatory: Disable CFI Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:58 ` Kees Cook 2022-05-14 21:58 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 19/21] x86/vdso: " Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 21:58 ` Kees Cook 2022-05-14 21:58 ` Kees Cook 2022-05-13 20:21 ` [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 22:02 ` Kees Cook 2022-05-14 22:02 ` Kees Cook 2022-05-16 18:57 ` Sami Tolvanen 2022-05-16 18:57 ` Sami Tolvanen 2022-05-15 3:19 ` Kees Cook 2022-05-15 3:19 ` Kees Cook 2022-05-16 8:32 ` David Laight 2022-05-16 8:32 ` David Laight 2022-05-16 16:39 ` Sami Tolvanen 2022-05-16 16:39 ` Sami Tolvanen 2022-05-16 21:32 ` David Laight 2022-05-16 21:32 ` David Laight 2022-05-16 21:44 ` Peter Zijlstra 2022-05-16 21:44 ` Peter Zijlstra 2022-05-16 22:03 ` Sami Tolvanen 2022-05-16 22:03 ` Sami Tolvanen 2022-05-17 6:44 ` Peter Zijlstra 2022-05-17 6:44 ` Peter Zijlstra 2022-05-17 20:36 ` Sami Tolvanen 2022-05-17 20:36 ` Sami Tolvanen 2022-05-17 7:56 ` David Laight 2022-05-17 7:56 ` David Laight 2022-05-16 9:54 ` Peter Zijlstra 2022-05-16 9:54 ` Peter Zijlstra 2022-05-16 11:45 ` Peter Zijlstra 2022-05-16 11:45 ` Peter Zijlstra 2022-05-16 12:58 ` Peter Zijlstra 2022-05-16 12:58 ` Peter Zijlstra 2022-05-20 13:49 ` Matthew Wilcox 2022-05-20 13:49 ` Matthew Wilcox 2022-05-16 17:15 ` Sami Tolvanen 2022-05-16 17:15 ` Sami Tolvanen 2022-05-16 18:30 ` Peter Zijlstra 2022-05-16 18:30 ` Peter Zijlstra 2022-05-16 19:39 ` Sami Tolvanen 2022-05-16 19:39 ` Sami Tolvanen 2022-05-16 20:37 ` Peter Zijlstra 2022-05-16 20:37 ` Peter Zijlstra 2022-05-25 20:02 ` Kees Cook 2022-05-25 20:02 ` Kees Cook 2022-05-16 22:59 ` Kees Cook 2022-05-16 22:59 ` Kees Cook 2022-05-17 8:05 ` Peter Zijlstra 2022-05-17 8:05 ` Peter Zijlstra 2022-05-17 8:32 ` Joao Moreira 2022-05-17 8:32 ` Joao Moreira 2022-05-17 8:40 ` Peter Zijlstra 2022-05-17 8:40 ` Peter Zijlstra 2022-05-17 8:48 ` David Laight 2022-05-17 8:48 ` David Laight 2022-05-17 9:38 ` Peter Zijlstra 2022-05-17 9:38 ` Peter Zijlstra 2022-05-13 20:21 ` [RFC PATCH v2 21/21] init: Drop __nocfi from __init Sami Tolvanen 2022-05-13 20:21 ` Sami Tolvanen 2022-05-14 22:03 ` Kees Cook 2022-05-14 22:03 ` Kees Cook 2022-05-16 17:16 ` Sami Tolvanen 2022-05-16 17:16 ` Sami Tolvanen [not found] ` <CA+icZUWr+-HjMvY1VZf+nqjTadxSTDciux0Y5Y-+p_j4o7CmXg@mail.gmail.com> 2022-05-16 17:57 ` [RFC PATCH v2 00/21] KCFI support Sami Tolvanen 2022-05-16 17:57 ` Sami Tolvanen 2022-05-17 7:33 ` Sedat Dilek 2022-05-17 7:33 ` Sedat Dilek 2022-05-17 18:49 ` Nathan Chancellor 2022-05-17 18:49 ` Nathan Chancellor 2022-05-19 9:01 ` Sedat Dilek 2022-05-19 9:01 ` Sedat Dilek 2022-05-19 20:26 ` Nathan Chancellor 2022-05-19 20:26 ` Nathan Chancellor 2022-05-19 20:41 ` Sami Tolvanen 2022-05-19 20:41 ` Sami Tolvanen 2022-05-17 8:57 ` Peter Zijlstra 2022-05-17 8:57 ` Peter Zijlstra 2022-05-17 20:25 ` Sami Tolvanen 2022-05-17 20:25 ` Sami Tolvanen
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