Commit 2bd926b4 authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

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: default avatarAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b938fcf4
......@@ -16,9 +16,13 @@
/* all clang versions usable with the kernel support KASAN ABI version 5 */
#define KASAN_ABI_VERSION 5
#if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
/* emulate gcc's __SANITIZE_ADDRESS__ flag */
#if __has_feature(address_sanitizer)
#define __SANITIZE_ADDRESS__
#define __no_sanitize_address \
__attribute__((no_sanitize("address", "hwaddress")))
#else
#define __no_sanitize_address
#endif
/*
......
......@@ -143,6 +143,12 @@
#define KASAN_ABI_VERSION 3
#endif
#if __has_attribute(__no_sanitize_address__)
#define __no_sanitize_address __attribute__((no_sanitize_address))
#else
#define __no_sanitize_address
#endif
#if GCC_VERSION >= 50100
#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
#endif
......
......@@ -199,19 +199,6 @@
*/
#define __noreturn __attribute__((__noreturn__))
/*
* Optional: only supported since gcc >= 4.8
* Optional: not supported by icc
*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fsanitize_005faddress-function-attribute
* clang: https://clang.llvm.org/docs/AttributeReference.html#no-sanitize-address-no-address-safety-analysis
*/
#if __has_attribute(__no_sanitize_address__)
# define __no_sanitize_address __attribute__((__no_sanitize_address__))
#else
# define __no_sanitize_address
#endif
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
* clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
......
......@@ -45,8 +45,6 @@ void kasan_free_pages(struct page *page, unsigned int order);
void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
slab_flags_t *flags);
void kasan_cache_shrink(struct kmem_cache *cache);
void kasan_cache_shutdown(struct kmem_cache *cache);
void kasan_poison_slab(struct page *page);
void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
......@@ -97,8 +95,6 @@ static inline void kasan_free_pages(struct page *page, unsigned int order) {}
static inline void kasan_cache_create(struct kmem_cache *cache,
unsigned int *size,
slab_flags_t *flags) {}
static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
static inline void kasan_poison_slab(struct page *page) {}
static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
......@@ -155,4 +151,16 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
#endif /* CONFIG_KASAN */
#ifdef CONFIG_KASAN_GENERIC
void kasan_cache_shrink(struct kmem_cache *cache);
void kasan_cache_shutdown(struct kmem_cache *cache);
#else /* CONFIG_KASAN_GENERIC */
static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
#endif /* CONFIG_KASAN_GENERIC */
#endif /* LINUX_KASAN_H */
# 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.
......@@ -2,6 +2,7 @@
KASAN_SANITIZE := n
UBSAN_SANITIZE_common.o := n
UBSAN_SANITIZE_generic.o := n
UBSAN_SANITIZE_tags.o := n
KCOV_INSTRUMENT := n
CFLAGS_REMOVE_generic.o = -pg
......@@ -10,5 +11,8 @@ CFLAGS_REMOVE_generic.o = -pg
CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
obj-y := common.o generic.o report.o init.o quarantine.o
obj-$(CONFIG_KASAN) := common.o init.o report.o
obj-$(CONFIG_KASAN_GENERIC) += generic.o quarantine.o
obj-$(CONFIG_KASAN_SW_TAGS) += tags.o
/*
* This file contains core KASAN code.
* This file contains core generic KASAN code.
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
......
......@@ -114,7 +114,8 @@ void kasan_report(unsigned long addr, size_t size,
bool is_write, unsigned long ip);
void kasan_report_invalid_free(void *object, unsigned long ip);
#if defined(CONFIG_SLAB) || defined(CONFIG_SLUB)
#if defined(CONFIG_KASAN_GENERIC) && \
(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
void quarantine_reduce(void);
void quarantine_remove_cache(struct kmem_cache *cache);
......
/*
* This file contains core tag-based KASAN code.
*
* Copyright (c) 2018 Google, Inc.
* Author: Andrey Konovalov <andreyknvl@google.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define DISABLE_BRANCH_PROFILING
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>
#include "kasan.h"
#include "../slab.h"
void check_memory_region(unsigned long addr, size_t size, bool write,
unsigned long ret_ip)
{
}
#define DEFINE_HWASAN_LOAD_STORE(size) \
void __hwasan_load##size##_noabort(unsigned long addr) \
{ \
} \
EXPORT_SYMBOL(__hwasan_load##size##_noabort); \
void __hwasan_store##size##_noabort(unsigned long addr) \
{ \
} \
EXPORT_SYMBOL(__hwasan_store##size##_noabort)
DEFINE_HWASAN_LOAD_STORE(1);
DEFINE_HWASAN_LOAD_STORE(2);
DEFINE_HWASAN_LOAD_STORE(4);
DEFINE_HWASAN_LOAD_STORE(8);
DEFINE_HWASAN_LOAD_STORE(16);
void __hwasan_loadN_noabort(unsigned long addr, unsigned long size)
{
}
EXPORT_SYMBOL(__hwasan_loadN_noabort);
void __hwasan_storeN_noabort(unsigned long addr, unsigned long size)
{
}
EXPORT_SYMBOL(__hwasan_storeN_noabort);
void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size)
{
}
EXPORT_SYMBOL(__hwasan_tag_memory);
......@@ -2992,7 +2992,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
do_slab_free(s, page, head, tail, cnt, addr);
}
#ifdef CONFIG_KASAN
#ifdef CONFIG_KASAN_GENERIC
void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr)
{
do_slab_free(cache, virt_to_head_page(x), x, NULL, 1, addr);
......
# SPDX-License-Identifier: GPL-2.0
ifdef CONFIG_KASAN
ifdef CONFIG_KASAN_GENERIC
ifdef CONFIG_KASAN_INLINE
call_threshold := 10000
else
......@@ -12,21 +13,15 @@ CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
ifneq ($(CONFIG_COMPILE_TEST),y)
$(warning Cannot use CONFIG_KASAN: \
-fsanitize=kernel-address is not supported by compiler)
endif
else
# -fasan-shadow-offset fails without -fsanitize
CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
# -fasan-shadow-offset fails without -fsanitize
CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
$(call cc-option, -fsanitize=kernel-address \
-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
else
else
# Now add all the compiler specific options that are valid standalone
CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
$(call cc-param,asan-globals=1) \
......@@ -34,14 +29,28 @@ else
$(call cc-param,asan-stack=1) \
$(call cc-param,asan-use-after-scope=1) \
$(call cc-param,asan-instrument-allocas=1)
endif
endif
ifdef CONFIG_KASAN_EXTRA
CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope)
endif
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
endif # CONFIG_KASAN_GENERIC
ifdef CONFIG_KASAN_SW_TAGS
ifdef CONFIG_KASAN_INLINE
instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
else
instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
endif
CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
-mllvm -hwasan-instrument-stack=0 \
$(instrumentation_flags)
endif # CONFIG_KASAN_SW_TAGS
ifdef CONFIG_KASAN
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
endif
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