mm/kasan: fix corruptions and false positive reports

[mirror_ubuntu-bionic-kernel.git] / mm / kasan / kasan.c

/*
 * This file contains shadow memory manipulation 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 <adech.fo@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.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define DISABLE_BRANCH_PROFILING

#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/slab.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/vmalloc.h>

#include "kasan.h"
#include "../slab.h"

/*
 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 */
static void kasan_poison_shadow(const void *address, size_t size, u8 value)
{
        void *shadow_start, *shadow_end;

        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)
{
        kasan_poison_shadow(address, size, 0);

        if (size & KASAN_SHADOW_MASK) {
                u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
                *shadow = size & KASAN_SHADOW_MASK;
        }
}

static void __kasan_unpoison_stack(struct task_struct *task, 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_remaining_stack(void *sp)
{
        __kasan_unpoison_stack(current, sp);
}

/*
 * All functions below always inlined so compiler could
 * perform better optimizations in each of __asan_loadX/__assn_storeX
 * depending on memory access size X.
 */

static __always_inline bool memory_is_poisoned_1(unsigned long addr)
{
        s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(shadow_value)) {
                s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
                return unlikely(last_accessible_byte >= shadow_value);
        }

        return false;
}

static __always_inline bool memory_is_poisoned_2(unsigned long addr)
{
        u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(*shadow_addr)) {
                if (memory_is_poisoned_1(addr + 1))
                        return true;

                /*
                 * If single shadow byte covers 2-byte access, we don't
                 * need to do anything more. Otherwise, test the first
                 * shadow byte.
                 */
                if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
                        return false;

                return unlikely(*(u8 *)shadow_addr);
        }

        return false;
}

static __always_inline bool memory_is_poisoned_4(unsigned long addr)
{
        u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(*shadow_addr)) {
                if (memory_is_poisoned_1(addr + 3))
                        return true;

                /*
                 * If single shadow byte covers 4-byte access, we don't
                 * need to do anything more. Otherwise, test the first
                 * shadow byte.
                 */
                if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
                        return false;

                return unlikely(*(u8 *)shadow_addr);
        }

        return false;
}

static __always_inline bool memory_is_poisoned_8(unsigned long addr)
{
        u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(*shadow_addr)) {
                if (memory_is_poisoned_1(addr + 7))
                        return true;

                /*
                 * If single shadow byte covers 8-byte access, we don't
                 * need to do anything more. Otherwise, test the first
                 * shadow byte.
                 */
                if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
                        return false;

                return unlikely(*(u8 *)shadow_addr);
        }

        return false;
}

static __always_inline bool memory_is_poisoned_16(unsigned long addr)
{
        u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);

        if (unlikely(*shadow_addr)) {
                u16 shadow_first_bytes = *(u16 *)shadow_addr;

                if (unlikely(shadow_first_bytes))
                        return true;

                /*
                 * If two shadow bytes covers 16-byte access, we don't
                 * need to do anything more. Otherwise, test the last
                 * shadow byte.
                 */
                if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
                        return false;

                return memory_is_poisoned_1(addr + 15);
        }

        return false;
}

static __always_inline unsigned long bytes_is_zero(const u8 *start,
                                        size_t size)
{
        while (size) {
                if (unlikely(*start))
                        return (unsigned long)start;
                start++;
                size--;
        }

        return 0;
}

static __always_inline unsigned long memory_is_zero(const void *start,
                                                const void *end)
{
        unsigned int words;
        unsigned long ret;
        unsigned int prefix = (unsigned long)start % 8;

        if (end - start <= 16)
                return bytes_is_zero(start, end - start);

        if (prefix) {
                prefix = 8 - prefix;
                ret = bytes_is_zero(start, prefix);
                if (unlikely(ret))
                        return ret;
                start += prefix;
        }

        words = (end - start) / 8;
        while (words) {
                if (unlikely(*(u64 *)start))
                        return bytes_is_zero(start, 8);
                start += 8;
                words--;
        }

        return bytes_is_zero(start, (end - start) % 8);
}

static __always_inline bool memory_is_poisoned_n(unsigned long addr,
                                                size_t size)
{
        unsigned long ret;

        ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
                        kasan_mem_to_shadow((void *)addr + size - 1) + 1);

        if (unlikely(ret)) {
                unsigned long last_byte = addr + size - 1;
                s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);

                if (unlikely(ret != (unsigned long)last_shadow ||
                        ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
                        return true;
        }
        return false;
}

static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
{
        if (__builtin_constant_p(size)) {
                switch (size) {
                case 1:
                        return memory_is_poisoned_1(addr);
                case 2:
                        return memory_is_poisoned_2(addr);
                case 4:
                        return memory_is_poisoned_4(addr);
                case 8:
                        return memory_is_poisoned_8(addr);
                case 16:
                        return memory_is_poisoned_16(addr);
                default:
                        BUILD_BUG();
                }
        }

        return memory_is_poisoned_n(addr, size);
}

static __always_inline void check_memory_region_inline(unsigned long addr,
                                                size_t size, bool write,
                                                unsigned long ret_ip)
{
        if (unlikely(size == 0))
                return;

        if (unlikely((void *)addr <
                kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
                kasan_report(addr, size, write, ret_ip);
                return;
        }

        if (likely(!memory_is_poisoned(addr, size)))
                return;

        kasan_report(addr, size, write, ret_ip);
}

static void check_memory_region(unsigned long addr,
                                size_t size, bool write,
                                unsigned long ret_ip)
{
        check_memory_region_inline(addr, size, write, ret_ip);
}

void kasan_check_read(const 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 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);
}

void kasan_alloc_pages(struct page *page, unsigned int order)
{
        if (likely(!PageHighMem(page)))
                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 size_t optimal_redzone(size_t object_size)
{
        int rz =
                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;
        return rz;
}

void kasan_cache_create(struct kmem_cache *cache, size_t *size,
                        unsigned long *flags)
{
        int redzone_adjust;
        int orig_size = *size;

        /* Add alloc meta. */
        cache->kasan_info.alloc_meta_offset = *size;
        *size += sizeof(struct kasan_alloc_meta);

        /* Add free meta. */
        if (cache->flags & SLAB_DESTROY_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_adjust = optimal_redzone(cache->object_size) -
                (*size - cache->object_size);

        if (redzone_adjust > 0)
                *size += redzone_adjust;

        *size = min(KMALLOC_MAX_SIZE, max(*size, cache->object_size +
                                        optimal_redzone(cache->object_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;
        }

        *flags |= SLAB_KASAN;
}

void kasan_cache_shrink(struct kmem_cache *cache)
{
        quarantine_remove_cache(cache);
}

void kasan_cache_destroy(struct kmem_cache *cache)
{
        quarantine_remove_cache(cache);
}

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);
}

void kasan_poison_slab(struct page *page)
{
        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);
        if (cache->flags & SLAB_KASAN) {
                struct kasan_alloc_meta *alloc_info =
                        get_alloc_info(cache, object);
                alloc_info->state = KASAN_STATE_INIT;
        }
}

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);
}

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_slab_alloc(struct kmem_cache *cache, void *object, gfp_t flags)
{
        kasan_kmalloc(cache, object, cache->object_size, flags);
}

static void kasan_poison_slab_free(struct kmem_cache *cache, void *object)
{
        unsigned long size = cache->object_size;
        unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);

        /* RCU slabs could be legally used after free within the RCU period */
        if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
                return;

        kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
}

bool kasan_slab_free(struct kmem_cache *cache, void *object)
{
        /* RCU slabs could be legally used after free within the RCU period */
        if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
                return false;

        if (likely(cache->flags & SLAB_KASAN)) {
                struct kasan_alloc_meta *alloc_info;
                struct kasan_free_meta *free_info;

                alloc_info = get_alloc_info(cache, object);
                free_info = get_free_info(cache, object);

                switch (alloc_info->state) {
                case KASAN_STATE_ALLOC:
                        alloc_info->state = KASAN_STATE_QUARANTINE;
                        set_track(&free_info->track, GFP_NOWAIT);
                        kasan_poison_slab_free(cache, object);
                        quarantine_put(free_info, cache);
                        return true;
                case KASAN_STATE_QUARANTINE:
                case KASAN_STATE_FREE:
                        pr_err("Double free");
                        dump_stack();
                        break;
                default:
                        break;
                }
        }
        return false;
}

void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size,
                   gfp_t flags)
{
        unsigned long redzone_start;
        unsigned long redzone_end;

        if (flags & __GFP_RECLAIM)
                quarantine_reduce();

        if (unlikely(object == NULL))
                return;

        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);

        kasan_unpoison_shadow(object, size);
        kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
                KASAN_KMALLOC_REDZONE);
        if (cache->flags & SLAB_KASAN) {
                struct kasan_alloc_meta *alloc_info =
                        get_alloc_info(cache, object);

                alloc_info->state = KASAN_STATE_ALLOC;
                alloc_info->alloc_size = size;
                set_track(&alloc_info->track, flags);
        }
}
EXPORT_SYMBOL(kasan_kmalloc);

void kasan_kmalloc_large(const void *ptr, size_t size, gfp_t flags)
{
        struct page *page;
        unsigned long redzone_start;
        unsigned long redzone_end;

        if (flags & __GFP_RECLAIM)
                quarantine_reduce();

        if (unlikely(ptr == NULL))
                return;

        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);
}

void kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
        struct page *page;

        if (unlikely(object == ZERO_SIZE_PTR))
                return;

        page = virt_to_head_page(object);

        if (unlikely(!PageSlab(page)))
                kasan_kmalloc_large(object, size, flags);
        else
                kasan_kmalloc(page->slab_cache, object, size, flags);
}

void kasan_poison_kfree(void *ptr)
{
        struct page *page;

        page = virt_to_head_page(ptr);

        if (unlikely(!PageSlab(page)))
                kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
                                KASAN_FREE_PAGE);
        else
                kasan_poison_slab_free(page->slab_cache, ptr);
}

void kasan_kfree_large(const void *ptr)
{
        struct page *page = virt_to_page(ptr);

        kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
                        KASAN_FREE_PAGE);
}

int kasan_module_alloc(void *addr, size_t size)
{
        void *ret;
        size_t shadow_size;
        unsigned long shadow_start;

        shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
        shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
                        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 | __GFP_HIGHMEM | __GFP_ZERO,
                        PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
                        __builtin_return_address(0));

        if (ret) {
                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));
}

static void register_global(struct kasan_global *global)
{
        size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);

        kasan_unpoison_shadow(global->beg, global->size);

        kasan_poison_shadow(global->beg + aligned_size,
                global->size_with_redzone - aligned_size,
                KASAN_GLOBAL_REDZONE);
}

void __asan_register_globals(struct kasan_global *globals, size_t size)
{
        int i;

        for (i = 0; i < size; i++)
                register_global(&globals[i]);
}
EXPORT_SYMBOL(__asan_register_globals);

void __asan_unregister_globals(struct kasan_global *globals, size_t size)
{
}
EXPORT_SYMBOL(__asan_unregister_globals);

#define DEFINE_ASAN_LOAD_STORE(size)                                    \
        void __asan_load##size(unsigned long addr)                      \
        {                                                               \
                check_memory_region_inline(addr, size, false, _RET_IP_);\
        }                                                               \
        EXPORT_SYMBOL(__asan_load##size);                               \
        __alias(__asan_load##size)                                      \
        void __asan_load##size##_noabort(unsigned long);                \
        EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
        void __asan_store##size(unsigned long addr)                     \
        {                                                               \
                check_memory_region_inline(addr, size, true, _RET_IP_); \
        }                                                               \
        EXPORT_SYMBOL(__asan_store##size);                              \
        __alias(__asan_store##size)                                     \
        void __asan_store##size##_noabort(unsigned long);               \
        EXPORT_SYMBOL(__asan_store##size##_noabort)

DEFINE_ASAN_LOAD_STORE(1);
DEFINE_ASAN_LOAD_STORE(2);
DEFINE_ASAN_LOAD_STORE(4);
DEFINE_ASAN_LOAD_STORE(8);
DEFINE_ASAN_LOAD_STORE(16);

void __asan_loadN(unsigned long addr, size_t size)
{
        check_memory_region(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_loadN);

__alias(__asan_loadN)
void __asan_loadN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_loadN_noabort);

void __asan_storeN(unsigned long addr, size_t size)
{
        check_memory_region(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_storeN);

__alias(__asan_storeN)
void __asan_storeN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_storeN_noabort);

/* to shut up compiler complaints */
void __asan_handle_no_return(void) {}
EXPORT_SYMBOL(__asan_handle_no_return);

#ifdef CONFIG_MEMORY_HOTPLUG
static int kasan_mem_notifier(struct notifier_block *nb,
                        unsigned long action, void *data)
{
        return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
}

static int __init kasan_memhotplug_init(void)
{
        pr_info("WARNING: KASAN doesn't support memory hot-add\n");
        pr_info("Memory hot-add will be disabled\n");

        hotplug_memory_notifier(kasan_mem_notifier, 0);

        return 0;
}

module_init(kasan_memhotplug_init);
#endif