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Diffstat (limited to 'mm/kasan/shadow.c')
| -rw-r--r-- | mm/kasan/shadow.c | 638 |
1 files changed, 638 insertions, 0 deletions
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c new file mode 100644 index 000000000000..9ef84f31833f --- /dev/null +++ b/mm/kasan/shadow.c @@ -0,0 +1,638 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This file contains KASAN runtime code that manages shadow memory for + * generic and software tag-based KASAN modes. + * + * Copyright (c) 2014 Samsung Electronics Co., Ltd. + * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> + * + * Some code borrowed from https://github.com/xairy/kasan-prototype by + * Andrey Konovalov <andreyknvl@gmail.com> + */ + +#include <linux/init.h> +#include <linux/kasan.h> +#include <linux/kernel.h> +#include <linux/kfence.h> +#include <linux/kmemleak.h> +#include <linux/memory.h> +#include <linux/mm.h> +#include <linux/string.h> +#include <linux/types.h> +#include <linux/vmalloc.h> + +#include <asm/cacheflush.h> +#include <asm/tlbflush.h> + +#include "kasan.h" + +bool __kasan_check_read(const volatile void *p, unsigned int size) +{ + return kasan_check_range((void *)p, size, false, _RET_IP_); +} +EXPORT_SYMBOL(__kasan_check_read); + +bool __kasan_check_write(const volatile void *p, unsigned int size) +{ + return kasan_check_range((void *)p, size, true, _RET_IP_); +} +EXPORT_SYMBOL(__kasan_check_write); + +#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY) +/* + * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be + * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions + * for the sites they want to instrument. + * + * If we have a compiler that can instrument meminstrinsics, never override + * these, so that non-instrumented files can safely consider them as builtins. + */ +#undef memset +void *memset(void *addr, int c, size_t len) +{ + if (!kasan_check_range(addr, len, true, _RET_IP_)) + return NULL; + + return __memset(addr, c, len); +} + +#ifdef __HAVE_ARCH_MEMMOVE +#undef memmove +void *memmove(void *dest, const void *src, size_t len) +{ + if (!kasan_check_range(src, len, false, _RET_IP_) || + !kasan_check_range(dest, len, true, _RET_IP_)) + return NULL; + + return __memmove(dest, src, len); +} +#endif + +#undef memcpy +void *memcpy(void *dest, const void *src, size_t len) +{ + if (!kasan_check_range(src, len, false, _RET_IP_) || + !kasan_check_range(dest, len, true, _RET_IP_)) + return NULL; + + return __memcpy(dest, src, len); +} +#endif + +void *__asan_memset(void *addr, int c, ssize_t len) +{ + if (!kasan_check_range(addr, len, true, _RET_IP_)) + return NULL; + + return __memset(addr, c, len); +} +EXPORT_SYMBOL(__asan_memset); + +#ifdef __HAVE_ARCH_MEMMOVE +void *__asan_memmove(void *dest, const void *src, ssize_t len) +{ + if (!kasan_check_range(src, len, false, _RET_IP_) || + !kasan_check_range(dest, len, true, _RET_IP_)) + return NULL; + + return __memmove(dest, src, len); +} +EXPORT_SYMBOL(__asan_memmove); +#endif + +void *__asan_memcpy(void *dest, const void *src, ssize_t len) +{ + if (!kasan_check_range(src, len, false, _RET_IP_) || + !kasan_check_range(dest, len, true, _RET_IP_)) + return NULL; + + return __memcpy(dest, src, len); +} +EXPORT_SYMBOL(__asan_memcpy); + +#ifdef CONFIG_KASAN_SW_TAGS +void *__hwasan_memset(void *addr, int c, ssize_t len) __alias(__asan_memset); +EXPORT_SYMBOL(__hwasan_memset); +#ifdef __HAVE_ARCH_MEMMOVE +void *__hwasan_memmove(void *dest, const void *src, ssize_t len) __alias(__asan_memmove); +EXPORT_SYMBOL(__hwasan_memmove); +#endif +void *__hwasan_memcpy(void *dest, const void *src, ssize_t len) __alias(__asan_memcpy); +EXPORT_SYMBOL(__hwasan_memcpy); +#endif + +void kasan_poison(const void *addr, size_t size, u8 value, bool init) +{ + void *shadow_start, *shadow_end; + + if (!kasan_arch_is_ready()) + return; + + /* + * Perform shadow offset calculation based on untagged address, as + * some of the callers (e.g. kasan_poison_new_object) pass tagged + * addresses to this function. + */ + addr = kasan_reset_tag(addr); + + if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) + return; + if (WARN_ON(size & KASAN_GRANULE_MASK)) + return; + + shadow_start = kasan_mem_to_shadow(addr); + shadow_end = kasan_mem_to_shadow(addr + size); + + __memset(shadow_start, value, shadow_end - shadow_start); +} +EXPORT_SYMBOL_GPL(kasan_poison); + +#ifdef CONFIG_KASAN_GENERIC +void kasan_poison_last_granule(const void *addr, size_t size) +{ + if (!kasan_arch_is_ready()) + return; + + if (size & KASAN_GRANULE_MASK) { + u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size); + *shadow = size & KASAN_GRANULE_MASK; + } +} +#endif + +void kasan_unpoison(const void *addr, size_t size, bool init) +{ + u8 tag = get_tag(addr); + + /* + * Perform shadow offset calculation based on untagged address, as + * some of the callers (e.g. kasan_unpoison_new_object) pass tagged + * addresses to this function. + */ + addr = kasan_reset_tag(addr); + + if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK)) + return; + + /* Unpoison all granules that cover the object. */ + kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false); + + /* Partially poison the last granule for the generic mode. */ + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + kasan_poison_last_granule(addr, size); +} + +#ifdef CONFIG_MEMORY_HOTPLUG +static bool shadow_mapped(unsigned long addr) +{ + pgd_t *pgd = pgd_offset_k(addr); + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + + if (pgd_none(*pgd)) + return false; + p4d = p4d_offset(pgd, addr); + if (p4d_none(*p4d)) + return false; + pud = pud_offset(p4d, addr); + if (pud_none(*pud)) + return false; + + /* + * We can't use pud_large() or pud_huge(), the first one is + * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse + * pud_bad(), if pud is bad then it's bad because it's huge. + */ + if (pud_bad(*pud)) + return true; + pmd = pmd_offset(pud, addr); + if (pmd_none(*pmd)) + return false; + + if (pmd_bad(*pmd)) + return true; + pte = pte_offset_kernel(pmd, addr); + return !pte_none(ptep_get(pte)); +} + +static int __meminit kasan_mem_notifier(struct notifier_block *nb, + unsigned long action, void *data) +{ + struct memory_notify *mem_data = data; + unsigned long nr_shadow_pages, start_kaddr, shadow_start; + unsigned long shadow_end, shadow_size; + + nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT; + start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn); + shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr); + shadow_size = nr_shadow_pages << PAGE_SHIFT; + shadow_end = shadow_start + shadow_size; + + if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) || + WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE)) + return NOTIFY_BAD; + + switch (action) { + case MEM_GOING_ONLINE: { + void *ret; + + /* + * If shadow is mapped already than it must have been mapped + * during the boot. This could happen if we onlining previously + * offlined memory. + */ + if (shadow_mapped(shadow_start)) + return NOTIFY_OK; + + ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start, + shadow_end, GFP_KERNEL, + PAGE_KERNEL, VM_NO_GUARD, + pfn_to_nid(mem_data->start_pfn), + __builtin_return_address(0)); + if (!ret) + return NOTIFY_BAD; + + kmemleak_ignore(ret); + return NOTIFY_OK; + } + case MEM_CANCEL_ONLINE: + case MEM_OFFLINE: { + struct vm_struct *vm; + + /* + * shadow_start was either mapped during boot by kasan_init() + * or during memory online by __vmalloc_node_range(). + * In the latter case we can use vfree() to free shadow. + * Non-NULL result of the find_vm_area() will tell us if + * that was the second case. + * + * Currently it's not possible to free shadow mapped + * during boot by kasan_init(). It's because the code + * to do that hasn't been written yet. So we'll just + * leak the memory. + */ + vm = find_vm_area((void *)shadow_start); + if (vm) + vfree((void *)shadow_start); + } + } + + return NOTIFY_OK; +} + +static int __init kasan_memhotplug_init(void) +{ + hotplug_memory_notifier(kasan_mem_notifier, DEFAULT_CALLBACK_PRI); + + return 0; +} + +core_initcall(kasan_memhotplug_init); +#endif + +#ifdef CONFIG_KASAN_VMALLOC + +void __init __weak kasan_populate_early_vm_area_shadow(void *start, + unsigned long size) +{ +} + +static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr, + void *unused) +{ + unsigned long page; + pte_t pte; + + if (likely(!pte_none(ptep_get(ptep)))) + return 0; + + page = __get_free_page(GFP_KERNEL); + if (!page) + return -ENOMEM; + + __memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE); + pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL); + + spin_lock(&init_mm.page_table_lock); + if (likely(pte_none(ptep_get(ptep)))) { + set_pte_at(&init_mm, addr, ptep, pte); + page = 0; + } + spin_unlock(&init_mm.page_table_lock); + if (page) + free_page(page); + return 0; +} + +int kasan_populate_vmalloc(unsigned long addr, unsigned long size) +{ + unsigned long shadow_start, shadow_end; + int ret; + + if (!kasan_arch_is_ready()) + return 0; + + if (!is_vmalloc_or_module_addr((void *)addr)) + return 0; + + shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); + shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); + + /* + * User Mode Linux maps enough shadow memory for all of virtual memory + * at boot, so doesn't need to allocate more on vmalloc, just clear it. + * + * The remaining CONFIG_UML checks in this file exist for the same + * reason. + */ + if (IS_ENABLED(CONFIG_UML)) { + __memset((void *)shadow_start, KASAN_VMALLOC_INVALID, shadow_end - shadow_start); + return 0; + } + + shadow_start = PAGE_ALIGN_DOWN(shadow_start); + shadow_end = PAGE_ALIGN(shadow_end); + + ret = apply_to_page_range(&init_mm, shadow_start, + shadow_end - shadow_start, + kasan_populate_vmalloc_pte, NULL); + if (ret) + return ret; + + flush_cache_vmap(shadow_start, shadow_end); + + /* + * We need to be careful about inter-cpu effects here. Consider: + * + * CPU#0 CPU#1 + * WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ; + * p[99] = 1; + * + * With compiler instrumentation, that ends up looking like this: + * + * CPU#0 CPU#1 + * // vmalloc() allocates memory + * // let a = area->addr + * // we reach kasan_populate_vmalloc + * // and call kasan_unpoison: + * STORE shadow(a), unpoison_val + * ... + * STORE shadow(a+99), unpoison_val x = LOAD p + * // rest of vmalloc process <data dependency> + * STORE p, a LOAD shadow(x+99) + * + * If there is no barrier between the end of unpoisoning the shadow + * and the store of the result to p, the stores could be committed + * in a different order by CPU#0, and CPU#1 could erroneously observe + * poison in the shadow. + * + * We need some sort of barrier between the stores. + * + * In the vmalloc() case, this is provided by a smp_wmb() in + * clear_vm_uninitialized_flag(). In the per-cpu allocator and in + * get_vm_area() and friends, the caller gets shadow allocated but + * doesn't have any pages mapped into the virtual address space that + * has been reserved. Mapping those pages in will involve taking and + * releasing a page-table lock, which will provide the barrier. + */ + + return 0; +} + +static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, + void *unused) +{ + unsigned long page; + + page = (unsigned long)__va(pte_pfn(ptep_get(ptep)) << PAGE_SHIFT); + + spin_lock(&init_mm.page_table_lock); + + if (likely(!pte_none(ptep_get(ptep)))) { + pte_clear(&init_mm, addr, ptep); + free_page(page); + } + spin_unlock(&init_mm.page_table_lock); + + return 0; +} + +/* + * Release the backing for the vmalloc region [start, end), which + * lies within the free region [free_region_start, free_region_end). + * + * This can be run lazily, long after the region was freed. It runs + * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap + * infrastructure. + * + * How does this work? + * ------------------- + * + * We have a region that is page aligned, labeled as A. + * That might not map onto the shadow in a way that is page-aligned: + * + * start end + * v v + * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc + * -------- -------- -------- -------- -------- + * | | | | | + * | | | /-------/ | + * \-------\|/------/ |/---------------/ + * ||| || + * |??AAAAAA|AAAAAAAA|AA??????| < shadow + * (1) (2) (3) + * + * First we align the start upwards and the end downwards, so that the + * shadow of the region aligns with shadow page boundaries. In the + * example, this gives us the shadow page (2). This is the shadow entirely + * covered by this allocation. + * + * Then we have the tricky bits. We want to know if we can free the + * partially covered shadow pages - (1) and (3) in the example. For this, + * we are given the start and end of the free region that contains this + * allocation. Extending our previous example, we could have: + * + * free_region_start free_region_end + * | start end | + * v v v v + * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc + * -------- -------- -------- -------- -------- + * | | | | | + * | | | /-------/ | + * \-------\|/------/ |/---------------/ + * ||| || + * |FFAAAAAA|AAAAAAAA|AAF?????| < shadow + * (1) (2) (3) + * + * Once again, we align the start of the free region up, and the end of + * the free region down so that the shadow is page aligned. So we can free + * page (1) - we know no allocation currently uses anything in that page, + * because all of it is in the vmalloc free region. But we cannot free + * page (3), because we can't be sure that the rest of it is unused. + * + * We only consider pages that contain part of the original region for + * freeing: we don't try to free other pages from the free region or we'd + * end up trying to free huge chunks of virtual address space. + * + * Concurrency + * ----------- + * + * How do we know that we're not freeing a page that is simultaneously + * being used for a fresh allocation in kasan_populate_vmalloc(_pte)? + * + * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running + * at the same time. While we run under free_vmap_area_lock, the population + * code does not. + * + * free_vmap_area_lock instead operates to ensure that the larger range + * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and + * the per-cpu region-finding algorithm both run under free_vmap_area_lock, + * no space identified as free will become used while we are running. This + * means that so long as we are careful with alignment and only free shadow + * pages entirely covered by the free region, we will not run in to any + * trouble - any simultaneous allocations will be for disjoint regions. + */ +void kasan_release_vmalloc(unsigned long start, unsigned long end, + unsigned long free_region_start, + unsigned long free_region_end) +{ + void *shadow_start, *shadow_end; + unsigned long region_start, region_end; + unsigned long size; + + if (!kasan_arch_is_ready()) + return; + + region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE); + region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE); + + free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE); + + if (start != region_start && + free_region_start < region_start) + region_start -= KASAN_MEMORY_PER_SHADOW_PAGE; + + free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE); + + if (end != region_end && + free_region_end > region_end) + region_end += KASAN_MEMORY_PER_SHADOW_PAGE; + + shadow_start = kasan_mem_to_shadow((void *)region_start); + shadow_end = kasan_mem_to_shadow((void *)region_end); + + if (shadow_end > shadow_start) { + size = shadow_end - shadow_start; + if (IS_ENABLED(CONFIG_UML)) { + __memset(shadow_start, KASAN_SHADOW_INIT, shadow_end - shadow_start); + return; + } + apply_to_existing_page_range(&init_mm, + (unsigned long)shadow_start, + size, kasan_depopulate_vmalloc_pte, + NULL); + flush_tlb_kernel_range((unsigned long)shadow_start, + (unsigned long)shadow_end); + } +} + +void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, + kasan_vmalloc_flags_t flags) +{ + /* + * Software KASAN modes unpoison both VM_ALLOC and non-VM_ALLOC + * mappings, so the KASAN_VMALLOC_VM_ALLOC flag is ignored. + * Software KASAN modes can't optimize zeroing memory by combining it + * with setting memory tags, so the KASAN_VMALLOC_INIT flag is ignored. + */ + + if (!kasan_arch_is_ready()) + return (void *)start; + + if (!is_vmalloc_or_module_addr(start)) + return (void *)start; + + /* + * Don't tag executable memory with the tag-based mode. + * The kernel doesn't tolerate having the PC register tagged. + */ + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) && + !(flags & KASAN_VMALLOC_PROT_NORMAL)) + return (void *)start; + + start = set_tag(start, kasan_random_tag()); + kasan_unpoison(start, size, false); + return (void *)start; +} + +/* + * Poison the shadow for a vmalloc region. Called as part of the + * freeing process at the time the region is freed. + */ +void __kasan_poison_vmalloc(const void *start, unsigned long size) +{ + if (!kasan_arch_is_ready()) + return; + + if (!is_vmalloc_or_module_addr(start)) + return; + + size = round_up(size, KASAN_GRANULE_SIZE); + kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); +} + +#else /* CONFIG_KASAN_VMALLOC */ + +int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask) +{ + void *ret; + size_t scaled_size; + size_t shadow_size; + unsigned long shadow_start; + + shadow_start = (unsigned long)kasan_mem_to_shadow(addr); + scaled_size = (size + KASAN_GRANULE_SIZE - 1) >> + KASAN_SHADOW_SCALE_SHIFT; + shadow_size = round_up(scaled_size, PAGE_SIZE); + + if (WARN_ON(!PAGE_ALIGNED(shadow_start))) + return -EINVAL; + + if (IS_ENABLED(CONFIG_UML)) { + __memset((void *)shadow_start, KASAN_SHADOW_INIT, shadow_size); + return 0; + } + + ret = __vmalloc_node_range(shadow_size, 1, shadow_start, + shadow_start + shadow_size, + GFP_KERNEL, + PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE, + __builtin_return_address(0)); + + if (ret) { + struct vm_struct *vm = find_vm_area(addr); + __memset(ret, KASAN_SHADOW_INIT, shadow_size); + vm->flags |= VM_KASAN; + kmemleak_ignore(ret); + + if (vm->flags & VM_DEFER_KMEMLEAK) + kmemleak_vmalloc(vm, size, gfp_mask); + + return 0; + } + + return -ENOMEM; +} + +void kasan_free_module_shadow(const struct vm_struct *vm) +{ + if (IS_ENABLED(CONFIG_UML)) + return; + + if (vm->flags & VM_KASAN) + vfree(kasan_mem_to_shadow(vm->addr)); +} + +#endif |