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Diffstat (limited to 'mm/kasan/common.c')
| -rw-r--r-- | mm/kasan/common.c | 697 |
1 files changed, 697 insertions, 0 deletions
diff --git a/mm/kasan/common.c b/mm/kasan/common.c new file mode 100644 index 000000000000..03d5d1374ca7 --- /dev/null +++ b/mm/kasan/common.c @@ -0,0 +1,697 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This file contains common generic and tag-based KASAN code. + * + * 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> + * + * 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. + * + */ + +#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/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" + +static inline int in_irqentry_text(unsigned long ptr) +{ + return (ptr >= (unsigned long)&__irqentry_text_start && + ptr < (unsigned long)&__irqentry_text_end) || + (ptr >= (unsigned long)&__softirqentry_text_start && + ptr < (unsigned long)&__softirqentry_text_end); +} + +static inline void filter_irq_stacks(struct stack_trace *trace) +{ + int i; + + if (!trace->nr_entries) + return; + for (i = 0; i < trace->nr_entries; i++) + if (in_irqentry_text(trace->entries[i])) { + /* Include the irqentry function into the stack. */ + trace->nr_entries = i + 1; + break; + } +} + +static inline depot_stack_handle_t save_stack(gfp_t flags) +{ + unsigned long entries[KASAN_STACK_DEPTH]; + struct stack_trace trace = { + .nr_entries = 0, + .entries = entries, + .max_entries = KASAN_STACK_DEPTH, + .skip = 0 + }; + + save_stack_trace(&trace); + filter_irq_stacks(&trace); + if (trace.nr_entries != 0 && + trace.entries[trace.nr_entries-1] == ULONG_MAX) + trace.nr_entries--; + + return depot_save_stack(&trace, flags); +} + +static inline void set_track(struct kasan_track *track, gfp_t flags) +{ + track->pid = current->pid; + track->stack = save_stack(flags); +} + +void kasan_enable_current(void) +{ + current->kasan_depth++; +} + +void kasan_disable_current(void) +{ + current->kasan_depth--; +} + +void kasan_check_read(const volatile void *p, unsigned int size) +{ + check_memory_region((unsigned long)p, size, false, _RET_IP_); +} +EXPORT_SYMBOL(kasan_check_read); + +void kasan_check_write(const volatile void *p, unsigned int size) +{ + check_memory_region((unsigned long)p, size, true, _RET_IP_); +} +EXPORT_SYMBOL(kasan_check_write); + +#undef memset +void *memset(void *addr, int c, size_t len) +{ + check_memory_region((unsigned long)addr, len, true, _RET_IP_); + + return __memset(addr, c, len); +} + +#undef memmove +void *memmove(void *dest, const void *src, size_t len) +{ + check_memory_region((unsigned long)src, len, false, _RET_IP_); + check_memory_region((unsigned long)dest, len, true, _RET_IP_); + + return __memmove(dest, src, len); +} + +#undef memcpy +void *memcpy(void *dest, const void *src, size_t len) +{ + check_memory_region((unsigned long)src, len, false, _RET_IP_); + check_memory_region((unsigned long)dest, len, true, _RET_IP_); + + return __memcpy(dest, src, len); +} + +/* + * Poisons the shadow memory for 'size' bytes starting from 'addr'. + * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE. + */ +void kasan_poison_shadow(const void *address, size_t size, u8 value) +{ + void *shadow_start, *shadow_end; + + /* + * 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. + */ + address = reset_tag(address); + + shadow_start = kasan_mem_to_shadow(address); + shadow_end = kasan_mem_to_shadow(address + size); + + __memset(shadow_start, value, shadow_end - shadow_start); +} + +void kasan_unpoison_shadow(const void *address, size_t size) +{ + u8 tag = get_tag(address); + + /* + * 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. + */ + address = reset_tag(address); + + kasan_poison_shadow(address, size, tag); + + if (size & KASAN_SHADOW_MASK) { + u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size); + + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + *shadow = tag; + else + *shadow = size & KASAN_SHADOW_MASK; + } +} + +static void __kasan_unpoison_stack(struct task_struct *task, const void *sp) +{ + void *base = task_stack_page(task); + size_t size = sp - base; + + kasan_unpoison_shadow(base, size); +} + +/* Unpoison the entire stack for a task. */ +void kasan_unpoison_task_stack(struct task_struct *task) +{ + __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE); +} + +/* Unpoison the stack for the current task beyond a watermark sp value. */ +asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) +{ + /* + * Calculate the task stack base address. Avoid using 'current' + * because this function is called by early resume code which hasn't + * yet set up the percpu register (%gs). + */ + void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1)); + + kasan_unpoison_shadow(base, watermark - base); +} + +/* + * Clear all poison for the region between the current SP and a provided + * watermark value, as is sometimes required prior to hand-crafted asm function + * returns in the middle of functions. + */ +void kasan_unpoison_stack_above_sp_to(const void *watermark) +{ + const void *sp = __builtin_frame_address(0); + size_t size = watermark - sp; + + if (WARN_ON(sp > watermark)) + return; + kasan_unpoison_shadow(sp, size); +} + +void kasan_alloc_pages(struct page *page, unsigned int order) +{ + u8 tag; + unsigned long i; + + if (unlikely(PageHighMem(page))) + return; + + tag = random_tag(); + for (i = 0; i < (1 << order); i++) + page_kasan_tag_set(page + i, tag); + kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order); +} + +void kasan_free_pages(struct page *page, unsigned int order) +{ + if (likely(!PageHighMem(page))) + kasan_poison_shadow(page_address(page), + PAGE_SIZE << order, + KASAN_FREE_PAGE); +} + +/* + * Adaptive redzone policy taken from the userspace AddressSanitizer runtime. + * For larger allocations larger redzones are used. + */ +static inline unsigned int optimal_redzone(unsigned int object_size) +{ + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + return 0; + + return + object_size <= 64 - 16 ? 16 : + object_size <= 128 - 32 ? 32 : + object_size <= 512 - 64 ? 64 : + object_size <= 4096 - 128 ? 128 : + object_size <= (1 << 14) - 256 ? 256 : + object_size <= (1 << 15) - 512 ? 512 : + object_size <= (1 << 16) - 1024 ? 1024 : 2048; +} + +void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, + slab_flags_t *flags) +{ + unsigned int orig_size = *size; + unsigned int redzone_size; + int redzone_adjust; + + /* Add alloc meta. */ + cache->kasan_info.alloc_meta_offset = *size; + *size += sizeof(struct kasan_alloc_meta); + + /* Add free meta. */ + if (IS_ENABLED(CONFIG_KASAN_GENERIC) && + (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor || + cache->object_size < sizeof(struct kasan_free_meta))) { + cache->kasan_info.free_meta_offset = *size; + *size += sizeof(struct kasan_free_meta); + } + + redzone_size = optimal_redzone(cache->object_size); + redzone_adjust = redzone_size - (*size - cache->object_size); + if (redzone_adjust > 0) + *size += redzone_adjust; + + *size = min_t(unsigned int, KMALLOC_MAX_SIZE, + max(*size, cache->object_size + redzone_size)); + + /* + * If the metadata doesn't fit, don't enable KASAN at all. + */ + if (*size <= cache->kasan_info.alloc_meta_offset || + *size <= cache->kasan_info.free_meta_offset) { + cache->kasan_info.alloc_meta_offset = 0; + cache->kasan_info.free_meta_offset = 0; + *size = orig_size; + return; + } + + cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE); + + *flags |= SLAB_KASAN; +} + +size_t kasan_metadata_size(struct kmem_cache *cache) +{ + return (cache->kasan_info.alloc_meta_offset ? + sizeof(struct kasan_alloc_meta) : 0) + + (cache->kasan_info.free_meta_offset ? + sizeof(struct kasan_free_meta) : 0); +} + +struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache, + const void *object) +{ + BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32); + return (void *)object + cache->kasan_info.alloc_meta_offset; +} + +struct kasan_free_meta *get_free_info(struct kmem_cache *cache, + const void *object) +{ + BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32); + return (void *)object + cache->kasan_info.free_meta_offset; +} + +void kasan_poison_slab(struct page *page) +{ + unsigned long i; + + for (i = 0; i < (1 << compound_order(page)); i++) + page_kasan_tag_reset(page + i); + kasan_poison_shadow(page_address(page), + PAGE_SIZE << compound_order(page), + KASAN_KMALLOC_REDZONE); +} + +void kasan_unpoison_object_data(struct kmem_cache *cache, void *object) +{ + kasan_unpoison_shadow(object, cache->object_size); +} + +void kasan_poison_object_data(struct kmem_cache *cache, void *object) +{ + kasan_poison_shadow(object, + round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE), + KASAN_KMALLOC_REDZONE); +} + +/* + * Since it's desirable to only call object contructors once during slab + * allocation, we preassign tags to all such objects. Also preassign tags for + * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports. + * For SLAB allocator we can't preassign tags randomly since the freelist is + * stored as an array of indexes instead of a linked list. Assign tags based + * on objects indexes, so that objects that are next to each other get + * different tags. + * After a tag is assigned, the object always gets allocated with the same tag. + * The reason is that we can't change tags for objects with constructors on + * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor + * code can save the pointer to the object somewhere (e.g. in the object + * itself). Then if we retag it, the old saved pointer will become invalid. + */ +static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new) +{ + if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU)) + return new ? KASAN_TAG_KERNEL : random_tag(); + +#ifdef CONFIG_SLAB + return (u8)obj_to_index(cache, virt_to_page(object), (void *)object); +#else + return new ? random_tag() : get_tag(object); +#endif +} + +void * __must_check kasan_init_slab_obj(struct kmem_cache *cache, + const void *object) +{ + struct kasan_alloc_meta *alloc_info; + + if (!(cache->flags & SLAB_KASAN)) + return (void *)object; + + alloc_info = get_alloc_info(cache, object); + __memset(alloc_info, 0, sizeof(*alloc_info)); + + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + object = set_tag(object, assign_tag(cache, object, true)); + + return (void *)object; +} + +void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object, + gfp_t flags) +{ + return kasan_kmalloc(cache, object, cache->object_size, flags); +} + +static inline bool shadow_invalid(u8 tag, s8 shadow_byte) +{ + if (IS_ENABLED(CONFIG_KASAN_GENERIC)) + return shadow_byte < 0 || + shadow_byte >= KASAN_SHADOW_SCALE_SIZE; + else + return tag != (u8)shadow_byte; +} + +static bool __kasan_slab_free(struct kmem_cache *cache, void *object, + unsigned long ip, bool quarantine) +{ + s8 shadow_byte; + u8 tag; + void *tagged_object; + unsigned long rounded_up_size; + + tag = get_tag(object); + tagged_object = object; + object = reset_tag(object); + + if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) != + object)) { + kasan_report_invalid_free(tagged_object, ip); + return true; + } + + /* RCU slabs could be legally used after free within the RCU period */ + if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU)) + return false; + + shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object)); + if (shadow_invalid(tag, shadow_byte)) { + kasan_report_invalid_free(tagged_object, ip); + return true; + } + + rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE); + kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE); + + if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) || + unlikely(!(cache->flags & SLAB_KASAN))) + return false; + + set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT); + quarantine_put(get_free_info(cache, object), cache); + + return IS_ENABLED(CONFIG_KASAN_GENERIC); +} + +bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) +{ + return __kasan_slab_free(cache, object, ip, true); +} + +void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object, + size_t size, gfp_t flags) +{ + unsigned long redzone_start; + unsigned long redzone_end; + u8 tag; + + if (gfpflags_allow_blocking(flags)) + quarantine_reduce(); + + if (unlikely(object == NULL)) + return NULL; + + redzone_start = round_up((unsigned long)(object + size), + KASAN_SHADOW_SCALE_SIZE); + redzone_end = round_up((unsigned long)object + cache->object_size, + KASAN_SHADOW_SCALE_SIZE); + + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + tag = assign_tag(cache, object, false); + + /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */ + kasan_unpoison_shadow(set_tag(object, tag), size); + kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start, + KASAN_KMALLOC_REDZONE); + + if (cache->flags & SLAB_KASAN) + set_track(&get_alloc_info(cache, object)->alloc_track, flags); + + return set_tag(object, tag); +} +EXPORT_SYMBOL(kasan_kmalloc); + +void * __must_check kasan_kmalloc_large(const void *ptr, size_t size, + gfp_t flags) +{ + struct page *page; + unsigned long redzone_start; + unsigned long redzone_end; + + if (gfpflags_allow_blocking(flags)) + quarantine_reduce(); + + if (unlikely(ptr == NULL)) + return NULL; + + page = virt_to_page(ptr); + redzone_start = round_up((unsigned long)(ptr + size), + KASAN_SHADOW_SCALE_SIZE); + redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page)); + + kasan_unpoison_shadow(ptr, size); + kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start, + KASAN_PAGE_REDZONE); + + return (void *)ptr; +} + +void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags) +{ + struct page *page; + + if (unlikely(object == ZERO_SIZE_PTR)) + return (void *)object; + + page = virt_to_head_page(object); + + if (unlikely(!PageSlab(page))) + return kasan_kmalloc_large(object, size, flags); + else + return kasan_kmalloc(page->slab_cache, object, size, flags); +} + +void kasan_poison_kfree(void *ptr, unsigned long ip) +{ + struct page *page; + + page = virt_to_head_page(ptr); + + if (unlikely(!PageSlab(page))) { + if (ptr != page_address(page)) { + kasan_report_invalid_free(ptr, ip); + return; + } + kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page), + KASAN_FREE_PAGE); + } else { + __kasan_slab_free(page->slab_cache, ptr, ip, false); + } +} + +void kasan_kfree_large(void *ptr, unsigned long ip) +{ + if (ptr != page_address(virt_to_head_page(ptr))) + kasan_report_invalid_free(ptr, ip); + /* The object will be poisoned by page_alloc. */ +} + +int kasan_module_alloc(void *addr, size_t size) +{ + 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_SHADOW_MASK) >> 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) { + __memset(ret, KASAN_SHADOW_INIT, shadow_size); + find_vm_area(addr)->flags |= VM_KASAN; + kmemleak_ignore(ret); + return 0; + } + + return -ENOMEM; +} + +void kasan_free_shadow(const struct vm_struct *vm) +{ + if (vm->flags & VM_KASAN) + vfree(kasan_mem_to_shadow(vm->addr)); +} + +#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_SHADOW_SCALE_SIZE) || + WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT))) + 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 |