// 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((unsigned long)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((unsigned long)p, size, true, _RET_IP_); } EXPORT_SYMBOL(__kasan_check_write); #undef memset void *memset(void *addr, int c, size_t len) { if (!kasan_check_range((unsigned long)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((unsigned long)src, len, false, _RET_IP_) || !kasan_check_range((unsigned long)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((unsigned long)src, len, false, _RET_IP_) || !kasan_check_range((unsigned long)dest, len, true, _RET_IP_)) return NULL; return __memcpy(dest, src, len); } 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_object_data) pass tagged * addresses to this function. */ addr = kasan_reset_tag(addr); /* Skip KFENCE memory if called explicitly outside of sl*b. */ if (is_kfence_address(addr)) return; 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(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_object_data) pass tagged * addresses to this function. */ addr = kasan_reset_tag(addr); /* * Skip KFENCE memory if called explicitly outside of sl*b. Also note * that calls to ksize(), where size is not a multiple of machine-word * size, would otherwise poison the invalid portion of the word. */ if (is_kfence_address(addr)) return; 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(*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, 0); 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))) 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))) { 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 (!is_vmalloc_or_module_addr((void *)addr)) return 0; shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE); shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); shadow_end = ALIGN(shadow_end, PAGE_SIZE); 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) << PAGE_SHIFT); spin_lock(&init_mm.page_table_lock); if (likely(!pte_none(*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; 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; 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 (!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 (!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; 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 (vm->flags & VM_KASAN) vfree(kasan_mem_to_shadow(vm->addr)); } #endif