|author||Kees Cook <email@example.com>||2019-04-10 08:48:31 -0700|
|committer||Kees Cook <firstname.lastname@example.org>||2019-04-24 14:00:56 -0700|
security: Implement Clang's stack initialization
CONFIG_INIT_STACK_ALL turns on stack initialization based on -ftrivial-auto-var-init in Clang builds, which has greater coverage than CONFIG_GCC_PLUGINS_STRUCTLEAK_BYREF_ALL. -ftrivial-auto-var-init Clang option provides trivial initializers for uninitialized local variables, variable fields and padding. It has three possible values: pattern - uninitialized locals are filled with a fixed pattern (mostly 0xAA on 64-bit platforms, see https://reviews.llvm.org/D54604 for more details, but 0x000000AA for 32-bit pointers) likely to cause crashes when uninitialized value is used; zero (it's still debated whether this flag makes it to the official Clang release) - uninitialized locals are filled with zeroes; uninitialized (default) - uninitialized locals are left intact. This patch uses only the "pattern" mode when CONFIG_INIT_STACK_ALL is enabled. Developers have the possibility to opt-out of this feature on a per-variable basis by using __attribute__((uninitialized)), but such use should be well justified in comments. Co-developed-by: Alexander Potapenko <email@example.com> Signed-off-by: Alexander Potapenko <firstname.lastname@example.org> Signed-off-by: Kees Cook <email@example.com> Tested-by: Alexander Potapenko <firstname.lastname@example.org> Acked-by: Masahiro Yamada <email@example.com>
Diffstat (limited to 'security')
1 files changed, 14 insertions, 0 deletions
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index a96d4a43ca65..0a1d4ca314f4 100644
@@ -18,9 +18,13 @@ config GCC_PLUGIN_STRUCTLEAK
menu "Memory initialization"
+ def_bool $(cc-option,-ftrivial-auto-var-init=pattern)
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
This option enables initialization of stack variables at
@@ -76,6 +80,16 @@ choice
of uninitialized stack variable exploits and information
+ config INIT_STACK_ALL
+ bool "0xAA-init everything on the stack (strongest)"
+ depends on CC_HAS_AUTO_VAR_INIT
+ Initializes everything on the stack with a 0xAA
+ pattern. 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.