diff --git a/Documentation/arm/memory.rst b/Documentation/arm/memory.rst index 34bb23c44a71..0cb1e2938823 100644 --- a/Documentation/arm/memory.rst +++ b/Documentation/arm/memory.rst @@ -77,6 +77,11 @@ MODULES_VADDR MODULES_END-1 Kernel module space Kernel modules inserted via insmod are placed here using dynamic mappings. +TASK_SIZE MODULES_VADDR-1 KASAn shadow memory when KASan is in use. + The range from MODULES_VADDR to the top + of the memory is shadowed here with 1 bit + per byte of memory. + 00001000 TASK_SIZE-1 User space mappings Per-thread mappings are placed here via the mmap() system call. diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index fe2f17eb2b50..194032568b7a 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1323,6 +1323,15 @@ config PAGE_OFFSET default 0xB0000000 if VMSPLIT_3G_OPT default 0xC0000000 +config KASAN_SHADOW_OFFSET + hex + depends on KASAN + default 0x1f000000 if PAGE_OFFSET=0x40000000 + default 0x5f000000 if PAGE_OFFSET=0x80000000 + default 0x9f000000 if PAGE_OFFSET=0xC0000000 + default 0x8f000000 if PAGE_OFFSET=0xB0000000 + default 0xffffffff + config NR_CPUS int "Maximum number of CPUs (2-32)" range 2 32 diff --git a/arch/arm/include/asm/kasan_def.h b/arch/arm/include/asm/kasan_def.h new file mode 100644 index 000000000000..5739605aa7cf --- /dev/null +++ b/arch/arm/include/asm/kasan_def.h @@ -0,0 +1,81 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/arm/include/asm/kasan_def.h + * + * Copyright (c) 2018 Huawei Technologies Co., Ltd. + * + * Author: Abbott Liu + */ + +#ifndef __ASM_KASAN_DEF_H +#define __ASM_KASAN_DEF_H + +#ifdef CONFIG_KASAN + +/* + * Define KASAN_SHADOW_OFFSET,KASAN_SHADOW_START and KASAN_SHADOW_END for + * the Arm kernel address sanitizer. We are "stealing" lowmem (the 4GB + * addressable by a 32bit architecture) out of the virtual address + * space to use as shadow memory for KASan as follows: + * + * +----+ 0xffffffff + * | | \ + * | | |-> Static kernel image (vmlinux) BSS and page table + * | |/ + * +----+ PAGE_OFFSET + * | | \ + * | | |-> Loadable kernel modules virtual address space area + * | |/ + * +----+ MODULES_VADDR = KASAN_SHADOW_END + * | | \ + * | | |-> The shadow area of kernel virtual address. + * | |/ + * +----+-> TASK_SIZE (start of kernel space) = KASAN_SHADOW_START the + * | |\ shadow address of MODULES_VADDR + * | | | + * | | | + * | | |-> The user space area in lowmem. The kernel address + * | | | sanitizer do not use this space, nor does it map it. + * | | | + * | | | + * | | | + * | | | + * | |/ + * ------ 0 + * + * 1) KASAN_SHADOW_START + * This value begins with the MODULE_VADDR's shadow address. It is the + * start of kernel virtual space. Since we have modules to load, we need + * to cover also that area with shadow memory so we can find memory + * bugs in modules. + * + * 2) KASAN_SHADOW_END + * This value is the 0x100000000's shadow address: the mapping that would + * be after the end of the kernel memory at 0xffffffff. It is the end of + * kernel address sanitizer shadow area. It is also the start of the + * module area. + * + * 3) KASAN_SHADOW_OFFSET: + * This value is used to map an address to the corresponding shadow + * address by the following formula: + * + * shadow_addr = (address >> 3) + KASAN_SHADOW_OFFSET; + * + * As you would expect, >> 3 is equal to dividing by 8, meaning each + * byte in the shadow memory covers 8 bytes of kernel memory, so one + * bit shadow memory per byte of kernel memory is used. + * + * The KASAN_SHADOW_OFFSET is provided in a Kconfig option depending + * on the VMSPLIT layout of the system: the kernel and userspace can + * split up lowmem in different ways according to needs, so we calculate + * the shadow offset depending on this. + */ + +#define KASAN_SHADOW_SCALE_SHIFT 3 +#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) +#define KASAN_SHADOW_END ((UL(1) << (32 - KASAN_SHADOW_SCALE_SHIFT)) \ + + KASAN_SHADOW_OFFSET) +#define KASAN_SHADOW_START ((KASAN_SHADOW_END >> 3) + KASAN_SHADOW_OFFSET) + +#endif +#endif diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h index bb79e52aeb90..598dbdca2017 100644 --- a/arch/arm/include/asm/memory.h +++ b/arch/arm/include/asm/memory.h @@ -18,6 +18,7 @@ #ifdef CONFIG_NEED_MACH_MEMORY_H #include #endif +#include /* PAGE_OFFSET - the virtual address of the start of the kernel image */ #define PAGE_OFFSET UL(CONFIG_PAGE_OFFSET) @@ -28,7 +29,11 @@ * TASK_SIZE - the maximum size of a user space task. * TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area */ +#ifndef CONFIG_KASAN #define TASK_SIZE (UL(CONFIG_PAGE_OFFSET) - UL(SZ_16M)) +#else +#define TASK_SIZE (KASAN_SHADOW_START) +#endif #define TASK_UNMAPPED_BASE ALIGN(TASK_SIZE / 3, SZ_16M) /* diff --git a/arch/arm/include/asm/uaccess-asm.h b/arch/arm/include/asm/uaccess-asm.h index 907571fd05c6..e6eb7a2aaf1e 100644 --- a/arch/arm/include/asm/uaccess-asm.h +++ b/arch/arm/include/asm/uaccess-asm.h @@ -85,7 +85,7 @@ */ .macro uaccess_entry, tsk, tmp0, tmp1, tmp2, disable ldr \tmp1, [\tsk, #TI_ADDR_LIMIT] - mov \tmp2, #TASK_SIZE + ldr \tmp2, =TASK_SIZE str \tmp2, [\tsk, #TI_ADDR_LIMIT] DACR( mrc p15, 0, \tmp0, c3, c0, 0) DACR( str \tmp0, [sp, #SVC_DACR]) diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 55a47df04773..c4220f51fcf3 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -427,7 +427,8 @@ ENDPROC(__fiq_abt) @ if it was interrupted in a critical region. Here we @ perform a quick test inline since it should be false @ 99.9999% of the time. The rest is done out of line. - cmp r4, #TASK_SIZE + ldr r0, =TASK_SIZE + cmp r4, r0 blhs kuser_cmpxchg64_fixup #endif #endif diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 271cb8a1eba1..fee279e28a72 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -50,7 +50,8 @@ __ret_fast_syscall: UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts ldr r2, [tsk, #TI_ADDR_LIMIT] - cmp r2, #TASK_SIZE + ldr r1, =TASK_SIZE + cmp r2, r1 blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK @@ -87,7 +88,8 @@ __ret_fast_syscall: #endif disable_irq_notrace @ disable interrupts ldr r2, [tsk, #TI_ADDR_LIMIT] - cmp r2, #TASK_SIZE + ldr r1, =TASK_SIZE + cmp r2, r1 blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK @@ -128,7 +130,8 @@ ret_slow_syscall: disable_irq_notrace @ disable interrupts ENTRY(ret_to_user_from_irq) ldr r2, [tsk, #TI_ADDR_LIMIT] - cmp r2, #TASK_SIZE + ldr r1, =TASK_SIZE + cmp r2, r1 blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] tst r1, #_TIF_WORK_MASK diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index fa259825310c..c06ebfbc48c4 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include @@ -1255,8 +1256,25 @@ static inline void prepare_page_table(void) /* * Clear out all the mappings below the kernel image. */ +#ifdef CONFIG_KASAN + /* + * KASan's shadow memory inserts itself between the TASK_SIZE + * and MODULES_VADDR. Do not clear the KASan shadow memory mappings. + */ + for (addr = 0; addr < KASAN_SHADOW_START; addr += PMD_SIZE) + pmd_clear(pmd_off_k(addr)); + /* + * Skip over the KASan shadow area. KASAN_SHADOW_END is sometimes + * equal to MODULES_VADDR and then we exit the pmd clearing. If we + * are using a thumb-compiled kernel, there there will be 8MB more + * to clear as KASan always offset to 16 MB below MODULES_VADDR. + */ + for (addr = KASAN_SHADOW_END; addr < MODULES_VADDR; addr += PMD_SIZE) + pmd_clear(pmd_off_k(addr)); +#else for (addr = 0; addr < MODULES_VADDR; addr += PMD_SIZE) pmd_clear(pmd_off_k(addr)); +#endif #ifdef CONFIG_XIP_KERNEL /* The XIP kernel is mapped in the module area -- skip over it */