diff options
| -rw-r--r-- | security/Kconfig.hardening | 52 |
1 files changed, 32 insertions, 20 deletions
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 023aea5e117c..90cbaff86e13 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -29,6 +29,7 @@ choice prompt "Initialize kernel stack variables at function entry" default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PATTERN + default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_PATTERN default INIT_STACK_NONE help This option enables initialization of stack variables at @@ -39,11 +40,11 @@ choice syscalls. This chooses the level of coverage over classes of potentially - uninitialized variables. The selected class will be + uninitialized variables. The selected class of variable will be initialized before use in a function. config INIT_STACK_NONE - bool "no automatic initialization (weakest)" + bool "no automatic stack variable initialization (weakest)" help Disable automatic stack variable initialization. This leaves the kernel vulnerable to the standard @@ -80,7 +81,7 @@ choice and is disallowed. config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL - bool "zero-init anything passed by reference (very strong)" + bool "zero-init everything passed by reference (very strong)" depends on GCC_PLUGINS depends on !(KASAN && KASAN_STACK) select GCC_PLUGIN_STRUCTLEAK @@ -91,33 +92,44 @@ choice of uninitialized stack variable exploits and information exposures. + As a side-effect, this keeps a lot of variables on the + stack that can otherwise be optimized out, so combining + this with CONFIG_KASAN_STACK can lead to a stack overflow + and is disallowed. + config INIT_STACK_ALL_PATTERN - bool "0xAA-init everything on the stack (strongest)" + bool "pattern-init everything (strongest)" 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 - of uninitialized stack variable exploits and information - exposures, even variables that were warned to have been - left uninitialized. + Initializes everything on the stack (including padding) + with a specific debug value. This is intended to eliminate + all classes of uninitialized stack variable exploits and + information exposures, even variables that were warned about + having 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. + non-NULL values, buffer sizes and indices are very big. The + pattern is situation-specific; Clang on 64-bit uses 0xAA + repeating for all types and padding except float and double + which use 0xFF repeating (-NaN). Clang on 32-bit uses 0xFF + repeating for all types and padding. config INIT_STACK_ALL_ZERO - bool "zero-init everything on the stack (strongest and safest)" + bool "zero-init everything (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. + Initializes everything on the stack (including padding) + with a zero value. This is intended to eliminate all + classes of uninitialized stack variable exploits and + information exposures, even variables that were warned + about having been left uninitialized. + + Zero initialization provides safe defaults for strings + (immediately NUL-terminated), pointers (NULL), indices + (index 0), and sizes (0 length), so it is therefore more + suitable as a production security mitigation than pattern + initialization. endchoice |