esp-idf/components/heap/multi_heap_poisoning.c

// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include <string.h>
#include <stddef.h>
#include <stdio.h>
#include <sys/param.h>
#include <multi_heap.h>
#include "multi_heap_internal.h"

/* Note: Keep platform-specific parts in this header, this source
   file should depend on libc only */
#include "multi_heap_platform.h"

/* Defines compile-time configuration macros */
#include "multi_heap_config.h"

#ifdef MULTI_HEAP_POISONING

/* Alias MULTI_HEAP_POISONING_SLOW to SLOW for better readabilty */
#ifdef SLOW
#error "external header has defined SLOW"
#endif
#ifdef MULTI_HEAP_POISONING_SLOW
#define SLOW 1
#endif

#define MALLOC_FILL_PATTERN 0xce
#define FREE_FILL_PATTERN 0xfe

#define HEAD_CANARY_PATTERN 0xABBA1234
#define TAIL_CANARY_PATTERN 0xBAAD5678

typedef struct {
    uint32_t head_canary;
    size_t alloc_size;
} poison_head_t;

typedef struct {
    uint32_t tail_canary;
} poison_tail_t;

#define POISON_OVERHEAD (sizeof(poison_head_t) + sizeof(poison_tail_t))

/* Given a "poisoned" region with pre-data header 'head', and actual data size 'alloc_size', fill in the head and tail
   region checks.

   Returns the pointer to the actual usable data buffer (ie after 'head')
*/
static uint8_t *poison_allocated_region(poison_head_t *head, size_t alloc_size)
{
    uint8_t *data = (uint8_t *)(&head[1]); /* start of data ie 'real' allocated buffer */
    poison_tail_t *tail = (poison_tail_t *)(data + alloc_size);
    head->alloc_size = alloc_size;
    head->head_canary = HEAD_CANARY_PATTERN;

    uint32_t tail_canary = TAIL_CANARY_PATTERN;
    if ((intptr_t)tail % sizeof(void *) == 0) {
        tail->tail_canary = tail_canary;
    } else {
        /* unaligned tail_canary */
        memcpy(&tail->tail_canary, &tail_canary, sizeof(uint32_t));
    }

    return data;
}

/* Given a pointer to some allocated data, check the head & tail poison structures (before & after it) that were
   previously injected by poison_allocated_region().

   Returns a pointer to the poison header structure, or NULL if the poison structures are corrupt.
*/
static poison_head_t *verify_allocated_region(void *data, bool print_errors)
{
    poison_head_t *head = (poison_head_t *)((intptr_t)data - sizeof(poison_head_t));
    poison_tail_t *tail = (poison_tail_t *)((intptr_t)data + head->alloc_size);

    /* check if the beginning of the data was overwritten */
    if (head->head_canary != HEAD_CANARY_PATTERN) {
        if (print_errors) {
            MULTI_HEAP_STDERR_PRINTF("CORRUPT HEAP: Bad head at %p. Expected 0x%08x got 0x%08x\n", &head->head_canary,
                   HEAD_CANARY_PATTERN, head->head_canary);
        }
        return NULL;
    }

    /* check if the end of the data was overrun */
    uint32_t canary;
    if ((intptr_t)tail % sizeof(void *) == 0) {
        canary = tail->tail_canary;
    } else {
        /* tail is unaligned */
        memcpy(&canary, &tail->tail_canary, sizeof(canary));
    }
    if (canary != TAIL_CANARY_PATTERN) {
        if (print_errors) {
            printf("CORRUPT HEAP: Bad tail at %p. Expected 0x%08x got 0x%08x\n", &tail->tail_canary,
                   TAIL_CANARY_PATTERN, canary);
        }
        return NULL;
    }

    return head;
}

#ifdef SLOW
/* Go through a region that should have the specified fill byte 'pattern',
   verify it.

   if expect_free is true, expect FREE_FILL_PATTERN otherwise MALLOC_FILL_PATTERN.

   if swap_pattern is true, swap patterns in the buffer (ie replace MALLOC_FILL_PATTERN with FREE_FILL_PATTERN, and vice versa.)

   Returns true if verification checks out.
*/
static bool verify_fill_pattern(void *data, size_t size, bool print_errors, bool expect_free, bool swap_pattern)
{
    const uint32_t FREE_FILL_WORD = (FREE_FILL_PATTERN << 24) | (FREE_FILL_PATTERN << 16) | (FREE_FILL_PATTERN << 8) | FREE_FILL_PATTERN;
    const uint32_t MALLOC_FILL_WORD = (MALLOC_FILL_PATTERN << 24) | (MALLOC_FILL_PATTERN << 16) | (MALLOC_FILL_PATTERN << 8) | MALLOC_FILL_PATTERN;

    const uint32_t EXPECT_WORD = expect_free ? FREE_FILL_WORD : MALLOC_FILL_WORD;
    const uint32_t REPLACE_WORD = expect_free ? MALLOC_FILL_WORD : FREE_FILL_WORD;
    bool valid = true;

    /* Use 4-byte operations as much as possible */
    if ((intptr_t)data % 4 == 0) {
        uint32_t *p = data;
        while (size >= 4) {
            if (*p != EXPECT_WORD) {
                if (print_errors) {
                    MULTI_HEAP_STDERR_PRINTF("CORRUPT HEAP: Invalid data at %p. Expected 0x%08x got 0x%08x\n", p, EXPECT_WORD, *p);
                }
                valid = false;
            }
            if (swap_pattern) {
                *p = REPLACE_WORD;
            }
            p++;
            size -= 4;
        }
        data = p;
    }

    uint8_t *p = data;
    for (int i = 0; i < size; i++) {
        if (p[i] != (uint8_t)EXPECT_WORD) {
            if (print_errors) {
                MULTI_HEAP_STDERR_PRINTF("CORRUPT HEAP: Invalid data at %p. Expected 0x%02x got 0x%02x\n", p, (uint8_t)EXPECT_WORD, *p);
            }
            valid = false;
        }
        if (swap_pattern) {
            p[i] = (uint8_t)REPLACE_WORD;
        }
    }
    return valid;
}
#endif

void *multi_heap_malloc(multi_heap_handle_t heap, size_t size)
{
    multi_heap_internal_lock(heap);
    poison_head_t *head = multi_heap_malloc_impl(heap, size + POISON_OVERHEAD);
    uint8_t *data = NULL;
    if (head != NULL) {
        data = poison_allocated_region(head, size);
#ifdef SLOW
        /* check everything we got back is FREE_FILL_PATTERN & swap for MALLOC_FILL_PATTERN */
        assert( verify_fill_pattern(data, size, true, true, true) );
#endif
    }

    multi_heap_internal_unlock(heap);
    return data;
}

void multi_heap_free(multi_heap_handle_t heap, void *p)
{
    if (p == NULL) {
        return;
    }
    multi_heap_internal_lock(heap);

    poison_head_t *head = verify_allocated_region(p, true);
    assert(head != NULL);

    #ifdef SLOW
    /* replace everything with FREE_FILL_PATTERN, including the poison head/tail */
    memset(head, FREE_FILL_PATTERN,
           head->alloc_size + POISON_OVERHEAD);
    #endif
    multi_heap_free_impl(heap, head);

    multi_heap_internal_unlock(heap);
}

void *multi_heap_realloc(multi_heap_handle_t heap, void *p, size_t size)
{
    poison_head_t *head = NULL;
    poison_head_t *new_head;
    void *result = NULL;

    if (p == NULL) {
        return multi_heap_malloc(heap, size);
    }
    if (size == 0) {
        multi_heap_free(heap, p);
        return NULL;
    }

    /* p != NULL, size != 0 */
    head = verify_allocated_region(p, true);
    assert(head != NULL);

    multi_heap_internal_lock(heap);

#ifndef SLOW
    new_head = multi_heap_realloc_impl(heap, head, size + POISON_OVERHEAD);
    if (new_head != NULL) {
        /* For "fast" poisoning, we only overwrite the head/tail of the new block so it's safe
           to poison, so no problem doing this even if realloc resized in place.
        */
        result = poison_allocated_region(new_head, size);
    }
#else // SLOW
    /* When slow poisoning is enabled, it becomes very fiddly to try and correctly fill memory when resizing in place
       (where the buffer may be moved (including to an overlapping address with the old buffer), grown, or shrunk in
       place.)

       For now we just malloc a new buffer, copy, and free. :|

       Note: If this ever changes, multi_heap defrag realloc test should be enabled.
    */
    size_t orig_alloc_size = head->alloc_size;

    new_head = multi_heap_malloc_impl(heap, size + POISON_OVERHEAD);
    if (new_head != NULL) {
        result = poison_allocated_region(new_head, size);
        memcpy(result, p, MIN(size, orig_alloc_size));
        multi_heap_free(heap, p);
    }
#endif

    multi_heap_internal_unlock(heap);

    return result;
}

size_t multi_heap_get_allocated_size(multi_heap_handle_t heap, void *p)
{
    poison_head_t *head = verify_allocated_region(p, true);
    assert(head != NULL);
    size_t result = multi_heap_get_allocated_size_impl(heap, head);
    if (result > 0) {
        return result - POISON_OVERHEAD;
    }
    return 0;
}

multi_heap_handle_t multi_heap_register(void *start, size_t size)
{
    if (start != NULL) {
        memset(start, FREE_FILL_PATTERN, size);
    }
    return multi_heap_register_impl(start, size);
}

static inline void subtract_poison_overhead(size_t *arg) {
    if (*arg > POISON_OVERHEAD) {
        *arg -= POISON_OVERHEAD;
    } else {
        *arg = 0;
    }
}

void multi_heap_get_info(multi_heap_handle_t heap, multi_heap_info_t *info)
{
    multi_heap_get_info_impl(heap, info);
    /* don't count the heap poison head & tail overhead in the allocated bytes size */
    info->total_allocated_bytes -= info->allocated_blocks * POISON_OVERHEAD;
    /* trim largest_free_block to account for poison overhead */
    subtract_poison_overhead(&info->largest_free_block);
    /* similarly, trim total_free_bytes so there's no suggestion that
       a block this big may be available. */
    subtract_poison_overhead(&info->total_free_bytes);
    subtract_poison_overhead(&info->minimum_free_bytes);
}

size_t multi_heap_free_size(multi_heap_handle_t heap)
{
    size_t r = multi_heap_free_size_impl(heap);
    subtract_poison_overhead(&r);
    return r;
}

size_t multi_heap_minimum_free_size(multi_heap_handle_t heap)
{
    size_t r = multi_heap_minimum_free_size_impl(heap);
    subtract_poison_overhead(&r);
    return r;
}

/* Internal hooks used by multi_heap to manage poisoning, while keeping some modularity */

bool multi_heap_internal_check_block_poisoning(void *start, size_t size, bool is_free, bool print_errors)
{
    if (is_free) {
#ifdef SLOW
        return verify_fill_pattern(start, size, print_errors, true, false);
#else
        return true; /* can only verify empty blocks in SLOW mode */
#endif
    } else {
        void *data = (void *)((intptr_t)start + sizeof(poison_head_t));
        poison_head_t *head = verify_allocated_region(data, print_errors);
        if (head != NULL && head->alloc_size > size - POISON_OVERHEAD) {
            /* block can be bigger than alloc_size, for reasons of alignment & fragmentation,
               but block can never be smaller than head->alloc_size... */
            if (print_errors) {
                MULTI_HEAP_STDERR_PRINTF("CORRUPT HEAP: Size at %p expected <=0x%08x got 0x%08x\n", &head->alloc_size,
                       size - POISON_OVERHEAD, head->alloc_size);
            }
            return false;
        }
        return head != NULL;
    }
}

void multi_heap_internal_poison_fill_region(void *start, size_t size, bool is_free)
{
    memset(start, is_free ? FREE_FILL_PATTERN : MALLOC_FILL_PATTERN, size);
}

#else // !MULTI_HEAP_POISONING

#ifdef MULTI_HEAP_POISONING_SLOW
#error "MULTI_HEAP_POISONING_SLOW requires MULTI_HEAP_POISONING"
#endif

#endif  // MULTI_HEAP_POISONING