diff options
| -rw-r--r-- | Makefile | 13 | ||||
| -rw-r--r-- | init/main.c | 12 | ||||
| -rw-r--r-- | security/Kconfig.hardening | 29 |
3 files changed, 43 insertions, 11 deletions
@@ -802,11 +802,20 @@ KBUILD_CFLAGS += -fomit-frame-pointer endif endif -# Initialize all stack variables with a pattern, if desired. -ifdef CONFIG_INIT_STACK_ALL +# Initialize all stack variables with a 0xAA pattern. +ifdef CONFIG_INIT_STACK_ALL_PATTERN KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern endif +# Initialize all stack variables with a zero value. +ifdef CONFIG_INIT_STACK_ALL_ZERO +# Future support for zero initialization is still being debated, see +# https://bugs.llvm.org/show_bug.cgi?id=45497. These flags are subject to being +# renamed or dropped. +KBUILD_CFLAGS += -ftrivial-auto-var-init=zero +KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang +endif + DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments) ifdef CONFIG_DEBUG_INFO diff --git a/init/main.c b/init/main.c index 0ead83e86b5a..9127b240fd26 100644 --- a/init/main.c +++ b/init/main.c @@ -779,14 +779,16 @@ static void __init report_meminit(void) { const char *stack; - if (IS_ENABLED(CONFIG_INIT_STACK_ALL)) - stack = "all"; + if (IS_ENABLED(CONFIG_INIT_STACK_ALL_PATTERN)) + stack = "all(pattern)"; + else if (IS_ENABLED(CONFIG_INIT_STACK_ALL_ZERO)) + stack = "all(zero)"; else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)) - stack = "byref_all"; + stack = "byref_all(zero)"; else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)) - stack = "byref"; + stack = "byref(zero)"; else if (IS_ENABLED(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)) - stack = "__user"; + stack = "__user(zero)"; else stack = "off"; diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index af4c979b38ee..269967c4fc1b 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -19,13 +19,16 @@ config GCC_PLUGIN_STRUCTLEAK menu "Memory initialization" -config CC_HAS_AUTO_VAR_INIT +config CC_HAS_AUTO_VAR_INIT_PATTERN def_bool $(cc-option,-ftrivial-auto-var-init=pattern) +config CC_HAS_AUTO_VAR_INIT_ZERO + def_bool $(cc-option,-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang) + choice prompt "Initialize kernel stack variables at function entry" default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS - default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT + default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PATTERN default INIT_STACK_NONE help This option enables initialization of stack variables at @@ -88,9 +91,9 @@ choice of uninitialized stack variable exploits and information exposures. - config INIT_STACK_ALL + config INIT_STACK_ALL_PATTERN bool "0xAA-init everything on the stack (strongest)" - depends on CC_HAS_AUTO_VAR_INIT + depends on CC_HAS_AUTO_VAR_INIT_PATTERN help Initializes everything on the stack with a 0xAA pattern. This is intended to eliminate all classes @@ -98,6 +101,24 @@ choice exposures, even variables that were warned to have been left uninitialized. + Pattern initialization is known to provoke many existing bugs + related to uninitialized locals, e.g. pointers receive + non-NULL values, buffer sizes and indices are very big. + + config INIT_STACK_ALL_ZERO + bool "zero-init everything on the stack (strongest and safest)" + depends on CC_HAS_AUTO_VAR_INIT_ZERO + help + Initializes everything on the stack with a zero + value. This is intended to eliminate all classes + of uninitialized stack variable exploits and information + exposures, even variables that were warned to have been + left uninitialized. + + Zero initialization provides safe defaults for strings, + pointers, indices and sizes, and is therefore + more suitable as a security mitigation measure. + endchoice config GCC_PLUGIN_STRUCTLEAK_VERBOSE |