From: Sami Tolvanen <samitolvanen@google.com>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.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,
Sami Tolvanen <samitolvanen@google.com>
Subject: [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG
Date: Fri, 13 May 2022 13:21:58 -0700 [thread overview]
Message-ID: <20220513202159.1550547-21-samitolvanen@google.com> (raw)
In-Reply-To: <20220513202159.1550547-1-samitolvanen@google.com>
With CONFIG_CFI_CLANG, the compiler injects a type preamble
immediately before each function and a check to validate the target
function type before indirect calls:
; type preamble
__cfi_function:
int3
int3
mov <id>, %eax
int3
int3
function:
...
; indirect call check
cmpl <id>, -6(%r11)
je .Ltmp1
ud2
.Ltmp1:
call __x86_indirect_thunk_r11
Define the __CFI_TYPE helper macro for manual type annotations in
assembly code, add error handling for the CFI ud2 traps, and allow
CONFIG_CFI_CLANG to be selected on x86_64.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/linkage.h | 12 +++++++
arch/x86/kernel/traps.c | 60 +++++++++++++++++++++++++++++++++-
3 files changed, 73 insertions(+), 1 deletion(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4bed3abf444d..2e73d0792d48 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -108,6 +108,8 @@ config X86
select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64
select ARCH_SUPPORTS_NUMA_BALANCING if X86_64
select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096
+ select ARCH_SUPPORTS_CFI_CLANG if X86_64
+ select ARCH_USES_CFI_TRAPS if X86_64 && CFI_CLANG
select ARCH_SUPPORTS_LTO_CLANG
select ARCH_SUPPORTS_LTO_CLANG_THIN
select ARCH_USE_BUILTIN_BSWAP
diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 85865f1645bd..0ee4a0af3974 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -25,6 +25,18 @@
#define RET ret
#endif
+#ifdef CONFIG_CFI_CLANG
+#define __CFI_TYPE(name) \
+ .fill 7, 1, 0xCC ASM_NL \
+ SYM_START(__cfi_##name, SYM_L_LOCAL, SYM_A_NONE) \
+ int3 ASM_NL \
+ int3 ASM_NL \
+ mov __kcfi_typeid_##name, %eax ASM_NL \
+ int3 ASM_NL \
+ int3 ASM_NL \
+ SYM_FUNC_END(__cfi_##name)
+#endif
+
#else /* __ASSEMBLY__ */
#ifdef CONFIG_SLS
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 1563fb995005..320e257eb4be 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -40,6 +40,7 @@
#include <linux/hardirq.h>
#include <linux/atomic.h>
#include <linux/ioasid.h>
+#include <linux/cfi.h>
#include <asm/stacktrace.h>
#include <asm/processor.h>
@@ -295,6 +296,62 @@ static inline void handle_invalid_op(struct pt_regs *regs)
ILL_ILLOPN, error_get_trap_addr(regs));
}
+#ifdef CONFIG_CFI_CLANG
+static void decode_cfi_insn(struct pt_regs *regs, unsigned long *target,
+ unsigned long *type)
+{
+ char buffer[MAX_INSN_SIZE];
+ struct insn insn;
+ int offset;
+
+ *target = *type = 0;
+
+ /*
+ * The compiler generates the following instruction sequence
+ * for indirect call checks:
+ *
+ * cmpl <id>, -6(%reg) ; 7 bytes
+ * je .Ltmp1 ; 2 bytes
+ * ud2 ; <- addr
+ * .Ltmp1:
+ *
+ * Both the type and the target address can be decoded from the
+ * cmpl instruction.
+ */
+ if (copy_from_kernel_nofault(buffer, (void *)regs->ip - 9, MAX_INSN_SIZE))
+ return;
+ if (insn_decode_kernel(&insn, buffer))
+ return;
+ if (insn.opcode.value != 0x81 || X86_MODRM_REG(insn.modrm.value) != 7)
+ return;
+
+ *type = insn.immediate.value;
+
+ offset = insn_get_modrm_rm_off(&insn, regs);
+ if (offset < 0)
+ return;
+
+ *target = *(unsigned long *)((void *)regs + offset);
+}
+
+static enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
+{
+ if (is_cfi_trap(regs->ip)) {
+ unsigned long target, type;
+
+ decode_cfi_insn(regs, &target, &type);
+ return report_cfi_failure(regs, regs->ip, target, type);
+ }
+
+ return BUG_TRAP_TYPE_NONE;
+}
+#else
+static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs)
+{
+ return BUG_TRAP_TYPE_NONE;
+}
+#endif /* CONFIG_CFI_CLANG */
+
static noinstr bool handle_bug(struct pt_regs *regs)
{
bool handled = false;
@@ -312,7 +369,8 @@ static noinstr bool handle_bug(struct pt_regs *regs)
*/
if (regs->flags & X86_EFLAGS_IF)
raw_local_irq_enable();
- if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN) {
+ if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN ||
+ handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) {
regs->ip += LEN_UD2;
handled = true;
}
--
2.36.0.550.gb090851708-goog
next prev parent reply other threads:[~2022-05-13 20:24 UTC|newest]
Thread overview: 87+ 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 ` [RFC PATCH v2 01/21] efi/libstub: Filter out CC_FLAGS_CFI Sami Tolvanen
2022-05-14 21:42 ` Kees Cook
2022-05-16 15:44 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 02/21] arm64/vdso: " Sami Tolvanen
2022-05-14 21:42 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 03/21] kallsyms: Ignore __kcfi_typeid_ Sami Tolvanen
2022-05-14 21:43 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 04/21] cfi: Remove CONFIG_CFI_CLANG_SHADOW Sami Tolvanen
2022-05-14 21:43 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 05/21] cfi: Drop __CFI_ADDRESSABLE Sami Tolvanen
2022-05-14 21:44 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 06/21] cfi: Switch to -fsanitize=kcfi Sami Tolvanen
2022-05-14 21:46 ` 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
2022-05-14 21:49 ` Kees Cook
2022-05-16 12:28 ` Rasmus Villemoes
2022-05-16 16:23 ` Sami Tolvanen
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
2022-05-14 21:50 ` Kees Cook
2022-05-16 15:44 ` Sami Tolvanen
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
2022-05-14 21:50 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 10/21] arm64: Add CFI error handling Sami Tolvanen
2022-05-14 21:51 ` Kees Cook
2022-05-16 16:24 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 11/21] arm64: Drop unneeded __nocfi attributes Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-16 16:28 ` Sami Tolvanen
2022-05-13 20:21 ` [RFC PATCH v2 12/21] treewide: Drop function_nocfi Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 13/21] treewide: Drop WARN_ON_FUNCTION_MISMATCH Sami Tolvanen
2022-05-14 21:54 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 14/21] treewide: Drop __cficanonical Sami Tolvanen
2022-05-14 21:56 ` Kees Cook
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
2022-05-14 21:56 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 16/21] x86/tools/relocs: Ignore __kcfi_typeid_ relocations Sami Tolvanen
2022-05-14 21:57 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 17/21] x86: Add types to indirectly called assembly functions Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 18/21] x86/purgatory: Disable CFI Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` [RFC PATCH v2 19/21] x86/vdso: " Sami Tolvanen
2022-05-14 21:58 ` Kees Cook
2022-05-13 20:21 ` Sami Tolvanen [this message]
2022-05-14 22:02 ` [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG Kees Cook
2022-05-16 18:57 ` Sami Tolvanen
2022-05-15 3:19 ` Kees Cook
2022-05-16 8:32 ` David Laight
2022-05-16 16:39 ` Sami Tolvanen
2022-05-16 21:32 ` David Laight
2022-05-16 21:44 ` Peter Zijlstra
2022-05-16 22:03 ` Sami Tolvanen
2022-05-17 6:44 ` Peter Zijlstra
2022-05-17 20:36 ` Sami Tolvanen
2022-05-17 7:56 ` David Laight
2022-05-16 9:54 ` Peter Zijlstra
2022-05-16 11:45 ` Peter Zijlstra
2022-05-16 12:58 ` Peter Zijlstra
2022-05-20 13:49 ` Matthew Wilcox
2022-05-16 17:15 ` Sami Tolvanen
2022-05-16 18:30 ` Peter Zijlstra
2022-05-16 19:39 ` Sami Tolvanen
2022-05-16 20:37 ` Peter Zijlstra
2022-05-25 20:02 ` Kees Cook
2022-05-16 22:59 ` Kees Cook
2022-05-17 8:05 ` Peter Zijlstra
2022-05-17 8:32 ` Joao Moreira
2022-05-17 8:40 ` Peter Zijlstra
2022-05-17 8:48 ` David Laight
2022-05-17 9:38 ` Peter Zijlstra
2022-05-13 20:21 ` [RFC PATCH v2 21/21] init: Drop __nocfi from __init Sami Tolvanen
2022-05-14 22:03 ` Kees Cook
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
2022-05-17 7:33 ` Sedat Dilek
2022-05-17 18:49 ` Nathan Chancellor
2022-05-19 9:01 ` Sedat Dilek
2022-05-19 20:26 ` Nathan Chancellor
2022-05-19 20:41 ` Sami Tolvanen
2022-05-17 8:57 ` Peter Zijlstra
2022-05-17 20:25 ` Sami Tolvanen
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