KASAN's tag-based mode defines multiple special tag values. They're reserved for: - Native kernel value. On arm64 it's 0xFF and it causes an early return in the tag checking function. - Invalid value. 0xFE marks an area as freed / unallocated. It's also the value that is used to initialize regions of shadow memory. - Max value. 0xFD is the highest value that can be randomly generated for a new tag. Metadata macro is also defined: - Tag width equal to 8. Tag-based mode on x86 is going to use 4 bit wide tags so all the above values need to be changed accordingly. Make tags arch specific for x86, risc-v and arm64. On x86 the values just lose the top 4 bits. Replace hardcoded kernel tag value and tag width with macros in KASAN's non-arch specific code. Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx> --- MAINTAINERS | 2 +- arch/arm64/include/asm/kasan-tags.h | 9 +++++++++ arch/riscv/include/asm/kasan-tags.h | 12 ++++++++++++ arch/riscv/include/asm/kasan.h | 4 ---- arch/x86/include/asm/kasan-tags.h | 9 +++++++++ include/linux/kasan-tags.h | 12 +++++++++++- include/linux/kasan.h | 4 +++- include/linux/mm.h | 6 +++--- include/linux/page-flags-layout.h | 7 +------ 9 files changed, 49 insertions(+), 16 deletions(-) create mode 100644 arch/arm64/include/asm/kasan-tags.h create mode 100644 arch/riscv/include/asm/kasan-tags.h create mode 100644 arch/x86/include/asm/kasan-tags.h diff --git a/MAINTAINERS b/MAINTAINERS index b878ddc99f94..45671faa3b6f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12227,7 +12227,7 @@ L: kasan-dev@xxxxxxxxxxxxxxxx S: Maintained B: https://bugzilla.kernel.org/buglist.cgi?component=Sanitizers&product=Memory%20Management F: Documentation/dev-tools/kasan.rst -F: arch/*/include/asm/*kasan.h +F: arch/*/include/asm/*kasan*.h F: arch/*/mm/kasan_init* F: include/linux/kasan*.h F: lib/Kconfig.kasan diff --git a/arch/arm64/include/asm/kasan-tags.h b/arch/arm64/include/asm/kasan-tags.h new file mode 100644 index 000000000000..9e835da95f6b --- /dev/null +++ b/arch/arm64/include/asm/kasan-tags.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_KASAN_TAGS_H +#define __ASM_KASAN_TAGS_H + +#define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ + +#define KASAN_TAG_WIDTH 8 + +#endif /* ASM_KASAN_TAGS_H */ diff --git a/arch/riscv/include/asm/kasan-tags.h b/arch/riscv/include/asm/kasan-tags.h new file mode 100644 index 000000000000..83d7dcc8af74 --- /dev/null +++ b/arch/riscv/include/asm/kasan-tags.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_KASAN_TAGS_H +#define __ASM_KASAN_TAGS_H + +#ifdef CONFIG_KASAN_SW_TAGS +#define KASAN_TAG_KERNEL 0x7f /* native kernel pointers tag */ +#endif + +#define KASAN_TAG_WIDTH 8 + +#endif /* ASM_KASAN_TAGS_H */ + diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h index f6b378ba936d..27938e0d5233 100644 --- a/arch/riscv/include/asm/kasan.h +++ b/arch/riscv/include/asm/kasan.h @@ -41,10 +41,6 @@ #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) -#ifdef CONFIG_KASAN_SW_TAGS -#define KASAN_TAG_KERNEL 0x7f /* native kernel pointers tag */ -#endif - #define arch_kasan_set_tag(addr, tag) __tag_set(addr, tag) #define arch_kasan_reset_tag(addr) __tag_reset(addr) #define arch_kasan_get_tag(addr) __tag_get(addr) diff --git a/arch/x86/include/asm/kasan-tags.h b/arch/x86/include/asm/kasan-tags.h new file mode 100644 index 000000000000..68ba385bc75c --- /dev/null +++ b/arch/x86/include/asm/kasan-tags.h @@ -0,0 +1,9 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_KASAN_TAGS_H +#define __ASM_KASAN_TAGS_H + +#define KASAN_TAG_KERNEL 0xF /* native kernel pointers tag */ + +#define KASAN_TAG_WIDTH 4 + +#endif /* ASM_KASAN_TAGS_H */ diff --git a/include/linux/kasan-tags.h b/include/linux/kasan-tags.h index e07c896f95d3..b4aacfa8709b 100644 --- a/include/linux/kasan-tags.h +++ b/include/linux/kasan-tags.h @@ -2,7 +2,17 @@ #ifndef _LINUX_KASAN_TAGS_H #define _LINUX_KASAN_TAGS_H -#include <asm/kasan.h> +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) +#include <asm/kasan-tags.h> +#endif + +#ifdef CONFIG_KASAN_SW_TAGS_DENSE +#define KASAN_TAG_WIDTH 4 +#endif + +#ifndef KASAN_TAG_WIDTH +#define KASAN_TAG_WIDTH 0 +#endif #ifndef KASAN_TAG_KERNEL #define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */ diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 5a3e9bec21c2..83146367170a 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -88,7 +88,9 @@ static inline u8 kasan_get_shadow_tag(const void *addr) #ifdef CONFIG_KASAN_SW_TAGS /* This matches KASAN_TAG_INVALID. */ -#define KASAN_SHADOW_INIT 0xFE +#ifndef KASAN_SHADOW_INIT +#define KASAN_SHADOW_INIT KASAN_TAG_INVALID +#endif #else #define KASAN_SHADOW_INIT 0 #endif diff --git a/include/linux/mm.h b/include/linux/mm.h index 61fff5d34ed5..ddca2f63a5f6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1813,7 +1813,7 @@ static inline u8 page_kasan_tag(const struct page *page) if (kasan_enabled()) { tag = (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK; - tag ^= 0xff; + tag ^= KASAN_TAG_KERNEL; } return tag; @@ -1826,7 +1826,7 @@ static inline void page_kasan_tag_set(struct page *page, u8 tag) if (!kasan_enabled()) return; - tag ^= 0xff; + tag ^= KASAN_TAG_KERNEL; old_flags = READ_ONCE(page->flags); do { flags = old_flags; @@ -1845,7 +1845,7 @@ static inline void page_kasan_tag_reset(struct page *page) static inline u8 page_kasan_tag(const struct page *page) { - return 0xff; + return KASAN_TAG_KERNEL; } static inline void page_kasan_tag_set(struct page *page, u8 tag) { } diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index 7d79818dc065..ac3576f409ad 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -3,6 +3,7 @@ #define PAGE_FLAGS_LAYOUT_H #include <linux/numa.h> +#include <linux/kasan-tags.h> #include <generated/bounds.h> /* @@ -72,12 +73,6 @@ #define NODE_NOT_IN_PAGE_FLAGS 1 #endif -#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) -#define KASAN_TAG_WIDTH 8 -#else -#define KASAN_TAG_WIDTH 0 -#endif - #ifdef CONFIG_NUMA_BALANCING #define LAST__PID_SHIFT 8 #define LAST__PID_MASK ((1 << LAST__PID_SHIFT)-1) -- 2.47.1
