From: Sami Tolvanen <samitolvanen@google.com>
To: 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>,
Steven Rostedt <rostedt@goodmis.org>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev, Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v5 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB
Date: Wed, 13 Oct 2021 11:16:47 -0700 [thread overview]
Message-ID: <20211013181658.1020262-5-samitolvanen@google.com> (raw)
In-Reply-To: <20211013181658.1020262-1-samitolvanen@google.com>
This change introduces the DEFINE_CFI_IMMEDIATE_RETURN_STUB macro,
which defines a stub function that immediately returns and when
defined in the core kernel, always passes indirect call checking
with CONFIG_CFI_CLANG. Note that this macro should only be used when
a stub cannot be called using the correct function type.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
---
include/asm-generic/vmlinux.lds.h | 11 +++++++++++
include/linux/cfi.h | 13 +++++++++++++
kernel/cfi.c | 24 +++++++++++++++++++++++-
3 files changed, 47 insertions(+), 1 deletion(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f2984af2b85b..5b77284f7221 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -407,6 +407,16 @@
KEEP(*(.static_call_tramp_key)) \
__stop_static_call_tramp_key = .;
+#ifdef CONFIG_CFI_CLANG
+#define CFI_EXCLUDED_DATA \
+ . = ALIGN(8); \
+ __start_cfi_excluded = .; \
+ KEEP(*(.cfi_excluded_stubs)) \
+ __stop_cfi_excluded = .;
+#else
+#define CFI_EXCLUDED_DATA
+#endif
+
/*
* Allow architectures to handle ro_after_init data on their
* own by defining an empty RO_AFTER_INIT_DATA.
@@ -430,6 +440,7 @@
__start_rodata = .; \
*(.rodata) *(.rodata.*) \
SCHED_DATA \
+ CFI_EXCLUDED_DATA \
RO_AFTER_INIT_DATA /* Read only after init */ \
. = ALIGN(8); \
__start___tracepoints_ptrs = .; \
diff --git a/include/linux/cfi.h b/include/linux/cfi.h
index 879744aaa6e0..19f74af8eac2 100644
--- a/include/linux/cfi.h
+++ b/include/linux/cfi.h
@@ -20,6 +20,17 @@ extern void __cfi_check(uint64_t id, void *ptr, void *diag);
#define __CFI_ADDRESSABLE(fn, __attr) \
const void *__cfi_jt_ ## fn __visible __attr = (void *)&fn
+/*
+ * Defines a stub function that returns immediately, and when defined and
+ * referenced in the core kernel, always passes CFI checking. This should
+ * be used only for stubs that cannot be called using the correct function
+ * pointer type, which should be rare.
+ */
+#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \
+ void fn(void) { return; } \
+ const void *__cfi_excl_ ## fn __visible \
+ __section(".cfi_excluded_stubs") = (void *)&fn
+
#ifdef CONFIG_CFI_CLANG_SHADOW
extern void cfi_module_add(struct module *mod, unsigned long base_addr);
@@ -35,6 +46,8 @@ static inline void cfi_module_remove(struct module *mod, unsigned long base_addr
#else /* !CONFIG_CFI_CLANG */
#define __CFI_ADDRESSABLE(fn, __attr)
+#define DEFINE_CFI_IMMEDIATE_RETURN_STUB(fn) \
+ void fn(void) { return; }
#endif /* CONFIG_CFI_CLANG */
diff --git a/kernel/cfi.c b/kernel/cfi.c
index 9594cfd1cf2c..8d931089141b 100644
--- a/kernel/cfi.c
+++ b/kernel/cfi.c
@@ -278,12 +278,34 @@ static inline cfi_check_fn find_module_check_fn(unsigned long ptr)
return fn;
}
+extern unsigned long __start_cfi_excluded[];
+extern unsigned long __stop_cfi_excluded[];
+
+static inline bool is_cfi_excluded(unsigned long ptr)
+{
+ unsigned long *p = __start_cfi_excluded;
+
+ for ( ; p < __stop_cfi_excluded; ++p)
+ if (*p == ptr)
+ return true;
+
+ return false;
+}
+
+static void __cfi_pass(uint64_t id, void *ptr, void *diag)
+{
+}
+
static inline cfi_check_fn find_check_fn(unsigned long ptr)
{
cfi_check_fn fn = NULL;
- if (is_kernel_text(ptr))
+ if (is_kernel_text(ptr)) {
+ if (unlikely(is_cfi_excluded(ptr)))
+ return __cfi_pass;
+
return __cfi_check;
+ }
/*
* Indirect call checks can happen when RCU is not watching. Both
--
2.33.0.1079.g6e70778dc9-goog
next prev parent reply other threads:[~2021-10-13 18:17 UTC|newest]
Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-13 18:16 [PATCH v5 00/15] x86: Add support for Clang CFI Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 01/15] objtool: Add CONFIG_CFI_CLANG support Sami Tolvanen
2021-10-13 18:59 ` Kees Cook
2021-10-14 0:44 ` Josh Poimboeuf
2021-10-14 10:22 ` Peter Zijlstra
2021-10-14 19:20 ` Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 02/15] objtool: Add ASM_STACK_FRAME_NON_STANDARD Sami Tolvanen
2021-10-13 18:59 ` Kees Cook
2021-10-13 18:16 ` [PATCH v5 03/15] linkage: Add DECLARE_NOT_CALLED_FROM_C Sami Tolvanen
2021-10-13 19:00 ` Kees Cook
2021-10-15 2:51 ` Andy Lutomirski
2021-10-15 15:35 ` Sami Tolvanen
2021-10-15 15:55 ` Thomas Gleixner
2021-10-15 16:22 ` Andy Lutomirski
2021-10-15 16:47 ` Sami Tolvanen
2021-10-15 17:34 ` Andy Lutomirski
2021-10-15 17:57 ` Thomas Gleixner
2021-10-15 18:42 ` Sami Tolvanen
2021-10-15 19:35 ` Andy Lutomirski
2021-10-15 20:37 ` Sami Tolvanen
2021-10-16 21:12 ` Josh Poimboeuf
2021-10-18 17:08 ` Sami Tolvanen
2021-10-15 22:17 ` Thomas Gleixner
2021-10-16 21:16 ` Josh Poimboeuf
2021-10-13 18:16 ` Sami Tolvanen [this message]
2021-10-13 19:02 ` [PATCH v5 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB Kees Cook
2021-10-13 18:16 ` [PATCH v5 05/15] tracepoint: Exclude tp_stub_func from CFI checking Sami Tolvanen
2021-10-13 19:03 ` Kees Cook
2021-10-13 19:20 ` Steven Rostedt
2021-10-13 18:16 ` [PATCH v5 06/15] ftrace: Use an opaque type for functions not callable from C Sami Tolvanen
2021-10-13 19:04 ` Kees Cook
2021-10-13 19:20 ` Steven Rostedt
2021-10-13 18:16 ` [PATCH v5 07/15] lkdtm: Disable UNSET_SMEP with CFI Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 08/15] lkdtm: Use an opaque type for lkdtm_rodata_do_nothing Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 09/15] x86: Use an opaque type for functions not callable from C Sami Tolvanen
2021-10-14 11:21 ` Borislav Petkov
2021-10-14 16:07 ` Kees Cook
2021-10-14 17:31 ` Borislav Petkov
2021-10-14 18:24 ` Sami Tolvanen
2021-10-14 19:00 ` Nick Desaulniers
2021-10-14 18:47 ` Kees Cook
2021-10-14 18:52 ` Steven Rostedt
2021-10-14 19:06 ` Josh Poimboeuf
2021-10-13 18:16 ` [PATCH v5 10/15] x86/purgatory: Disable CFI Sami Tolvanen
2021-10-13 19:05 ` Kees Cook
2021-10-13 18:16 ` [PATCH v5 11/15] x86, relocs: Ignore __typeid__ relocations Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 12/15] x86, module: " Sami Tolvanen
2021-10-13 18:55 ` Kees Cook
2021-10-13 18:16 ` [PATCH v5 13/15] x86, cpu: Use LTO for cpu.c with CFI Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 14/15] x86, kprobes: Fix optprobe_template_func type mismatch Sami Tolvanen
2021-10-13 18:16 ` [PATCH v5 15/15] x86, build: Allow CONFIG_CFI_CLANG to be selected Sami Tolvanen
2021-10-13 18:56 ` Kees Cook
2021-10-13 19:07 ` [PATCH v5 00/15] x86: Add support for Clang CFI Kees Cook
2021-10-19 10:06 ` Alexander Lobakin
2021-10-19 15:40 ` Sami Tolvanen
2021-10-21 10:27 ` Alexander Lobakin
2021-10-26 20:16 ` Peter Zijlstra
2021-10-27 10:02 ` David Laight
2021-10-27 10:17 ` Peter Zijlstra
2021-10-27 12:05 ` Mark Rutland
2021-10-27 12:22 ` Ard Biesheuvel
2021-10-27 12:48 ` Peter Zijlstra
2021-10-27 13:04 ` Peter Zijlstra
2021-10-27 13:30 ` Ard Biesheuvel
2021-10-27 14:03 ` Peter Zijlstra
2021-10-27 14:18 ` Ard Biesheuvel
2021-10-27 14:36 ` Peter Zijlstra
2021-10-27 15:50 ` Sami Tolvanen
2021-10-27 15:55 ` Ard Biesheuvel
2021-10-29 20:03 ` Peter Zijlstra
2021-10-30 7:47 ` [PATCH] static_call,x86: Robustify trampoline patching Peter Zijlstra
2021-10-30 8:16 ` Peter Zijlstra
2021-11-02 17:35 ` Kees Cook
2021-11-02 18:15 ` Peter Zijlstra
2021-11-15 13:09 ` Rasmus Villemoes
2021-10-30 17:19 ` Ard Biesheuvel
2021-10-30 18:02 ` Peter Zijlstra
2021-10-30 18:55 ` Ard Biesheuvel
2021-10-31 16:24 ` Ard Biesheuvel
2021-10-31 16:39 ` Peter Zijlstra
2021-10-31 16:44 ` Ard Biesheuvel
2021-10-31 20:09 ` Peter Zijlstra
2021-10-31 20:21 ` Ard Biesheuvel
2021-10-31 20:44 ` Peter Zijlstra
2021-10-31 23:36 ` Ard Biesheuvel
2021-11-01 9:01 ` Peter Zijlstra
2021-11-01 9:36 ` David Laight
2021-11-01 14:14 ` Ard Biesheuvel
2021-11-02 12:57 ` Peter Zijlstra
2021-11-02 15:15 ` Peter Zijlstra
2021-11-02 17:44 ` Ard Biesheuvel
2021-11-02 18:14 ` Peter Zijlstra
2021-11-02 18:17 ` Peter Zijlstra
2021-11-02 18:18 ` Ard Biesheuvel
2021-11-02 21:48 ` Peter Zijlstra
2021-11-02 18:10 ` Kees Cook
2021-11-02 21:02 ` Andy Lutomirski
2021-11-02 23:13 ` Kees Cook
2021-11-03 0:20 ` Andy Lutomirski
2021-11-03 8:35 ` Peter Zijlstra
2021-11-03 10:01 ` David Laight
2021-11-03 19:32 ` Andy Lutomirski
2021-11-02 21:19 ` Peter Zijlstra
2021-11-11 12:15 ` [tip: locking/urgent] " tip-bot2 for Peter Zijlstra
2021-10-30 19:07 ` [PATCH v5 00/15] x86: Add support for Clang CFI Sami Tolvanen
2021-10-27 17:11 ` Kees Cook
2021-10-27 21:21 ` Peter Zijlstra
2021-10-27 22:27 ` Kees Cook
2021-10-28 11:09 ` Peter Zijlstra
2021-10-28 17:12 ` Kees Cook
2021-10-28 20:29 ` Peter Zijlstra
2021-11-02 17:26 ` Kees Cook
2021-11-01 4:13 ` Andy Lutomirski
2021-10-27 12:46 ` Peter Zijlstra
2021-10-27 12:55 ` David Laight
2021-10-27 13:17 ` Mark Rutland
2021-10-27 21:31 ` David Laight
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