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-rw-r--r--Makefile13
-rw-r--r--init/main.c12
-rw-r--r--security/Kconfig.hardening29
3 files changed, 43 insertions, 11 deletions
diff --git a/Makefile b/Makefile
index ae5d8220f431..d1cfbe5abc49 100644
--- a/Makefile
+++ b/Makefile
@@ -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