From 2bd926b439b4cb6b9ed240a9781cd01958b53d85 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Fri, 28 Dec 2018 00:29:53 -0800 Subject: kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS This commit splits the current CONFIG_KASAN config option into two: 1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one that exists now); 2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode. The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have another hardware tag-based KASAN mode, that will rely on hardware memory tagging support in arm64. With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to instrument kernel files with -fsantize=kernel-hwaddress (except the ones for which KASAN_SANITIZE := n is set). Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes. This commit also adds empty placeholder (for now) implementation of tag-based KASAN specific hooks inserted by the compiler and adjusts common hooks implementation. While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will enable once all the infrastracture code has been added. Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Andrey Ryabinin Reviewed-by: Dmitry Vyukov Cc: Christoph Lameter Cc: Mark Rutland Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/Kconfig.kasan | 98 ++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 76 insertions(+), 22 deletions(-) (limited to 'lib/Kconfig.kasan') diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index d0bad1bd9a2b..d8c474b6691e 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -1,36 +1,92 @@ +# This config refers to the generic KASAN mode. config HAVE_ARCH_KASAN bool -if HAVE_ARCH_KASAN +config HAVE_ARCH_KASAN_SW_TAGS + bool + +config CC_HAS_KASAN_GENERIC + def_bool $(cc-option, -fsanitize=kernel-address) + +config CC_HAS_KASAN_SW_TAGS + def_bool $(cc-option, -fsanitize=kernel-hwaddress) config KASAN - bool "KASan: runtime memory debugger" + bool "KASAN: runtime memory debugger" + depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ + (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS) + depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) + help + Enables KASAN (KernelAddressSANitizer) - runtime memory debugger, + designed to find out-of-bounds accesses and use-after-free bugs. + See Documentation/dev-tools/kasan.rst for details. + +choice + prompt "KASAN mode" + depends on KASAN + default KASAN_GENERIC + help + KASAN has two modes: generic KASAN (similar to userspace ASan, + x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and + software tag-based KASAN (a version based on software memory + tagging, arm64 only, similar to userspace HWASan, enabled with + CONFIG_KASAN_SW_TAGS). + Both generic and tag-based KASAN are strictly debugging features. + +config KASAN_GENERIC + bool "Generic mode" + depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) select SLUB_DEBUG if SLUB select CONSTRUCTORS select STACKDEPOT help - Enables kernel address sanitizer - runtime memory debugger, - designed to find out-of-bounds accesses and use-after-free bugs. - This is strictly a debugging feature and it requires a gcc version - of 4.9.2 or later. Detection of out of bounds accesses to stack or - global variables requires gcc 5.0 or later. - This feature consumes about 1/8 of available memory and brings about - ~x3 performance slowdown. + Enables generic KASAN mode. + Supported in both GCC and Clang. With GCC it requires version 4.9.2 + or later for basic support and version 5.0 or later for detection of + out-of-bounds accesses for stack and global variables and for inline + instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires + version 3.7.0 or later and it doesn't support detection of + out-of-bounds accesses for global variables yet. + This mode consumes about 1/8th of available memory at kernel start + and introduces an overhead of ~x1.5 for the rest of the allocations. + The performance slowdown is ~x3. For better error detection enable CONFIG_STACKTRACE. - Currently CONFIG_KASAN doesn't work with CONFIG_DEBUG_SLAB + Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB (the resulting kernel does not boot). +config KASAN_SW_TAGS + bool "Software tag-based mode" + depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS + depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) + select SLUB_DEBUG if SLUB + select CONSTRUCTORS + select STACKDEPOT + help + Enables software tag-based KASAN mode. + This mode requires Top Byte Ignore support by the CPU and therefore + is only supported for arm64. + This mode requires Clang version 7.0.0 or later. + This mode consumes about 1/16th of available memory at kernel start + and introduces an overhead of ~20% for the rest of the allocations. + This mode may potentially introduce problems relating to pointer + casting and comparison, as it embeds tags into the top byte of each + pointer. + For better error detection enable CONFIG_STACKTRACE. + Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB + (the resulting kernel does not boot). + +endchoice + config KASAN_EXTRA - bool "KAsan: extra checks" - depends on KASAN && DEBUG_KERNEL && !COMPILE_TEST + bool "KASAN: extra checks" + depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST help - This enables further checks in the kernel address sanitizer, for now - it only includes the address-use-after-scope check that can lead - to excessive kernel stack usage, frame size warnings and longer + This enables further checks in generic KASAN, for now it only + includes the address-use-after-scope check that can lead to + excessive kernel stack usage, frame size warnings and longer compile time. - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more - + See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 choice prompt "Instrumentation type" @@ -53,7 +109,7 @@ config KASAN_INLINE memory accesses. This is faster than outline (in some workloads it gives about x2 boost over outline instrumentation), but make kernel's .text size much bigger. - This requires a gcc version of 5.0 or later. + For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later. endchoice @@ -67,11 +123,9 @@ config KASAN_S390_4_LEVEL_PAGING 4-level paging instead. config TEST_KASAN - tristate "Module for testing kasan for bug detection" + tristate "Module for testing KASAN for bug detection" depends on m && KASAN help This is a test module doing various nasty things like out of bounds accesses, use after free. It is useful for testing - kernel debugging features like kernel address sanitizer. - -endif + kernel debugging features like KASAN. -- cgit v1.2.3