alloc-inl.h

/*
  Copyright 2013 Google Inc. All rights reserved.

  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.
*/

/*
   american fuzzy lop - error-checking, memory-zeroing alloc routines
   ------------------------------------------------------------------

   Written and maintained by Michal Zalewski <lcamtuf@google.com>

   This allocator is not designed to resist malicious attackers (the canaries
   are small and predictable), but provides a robust and portable way to detect
   use-after-free, off-by-one writes, stale pointers, and so on.
*/

#ifndef _HAVE_ALLOC_INL_H
#define _HAVE_ALLOC_INL_H

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "config.h"
#include "types.h"
#include "debug.h"

/* User-facing macro to sprintf() to a dynamically allocated buffer. */

#define alloc_printf(_str...) ({ \
    u8* _tmp; \
    s32 _len = snprintf(NULL, 0, _str); \
    if (_len < 0) FATAL("Whoa, snprintf() fails?!"); \
    _tmp = ck_alloc(_len + 1); \
    snprintf((char*)_tmp, _len + 1, _str); \
    _tmp; \
  })

/* Macro to enforce allocation limits as a last-resort defense against
   integer overflows. */

#define ALLOC_CHECK_SIZE(_s) do { \
    if ((_s) > MAX_ALLOC) \
      ABORT("Bad alloc request: %u bytes", (_s)); \
  } while (0)

/* Macro to check malloc() failures and the like. */

#define ALLOC_CHECK_RESULT(_r, _s) do { \
    if (!(_r)) \
      ABORT("Out of memory: can't allocate %u bytes", (_s)); \
  } while (0)

/* Magic tokens used to mark used / freed chunks. */

#define ALLOC_MAGIC_C1  0xFF00FF00 /* Used head (dword)  */
#define ALLOC_MAGIC_F   0xFE00FE00 /* Freed head (dword) */
#define ALLOC_MAGIC_C2  0xF0       /* Used tail (byte)   */

/* Positions of guard tokens in relation to the user-visible pointer. */

#define ALLOC_C1(_ptr)  (((u32*)(_ptr))[-2])
#define ALLOC_S(_ptr)   (((u32*)(_ptr))[-1])
#define ALLOC_C2(_ptr)  (((u8*)(_ptr))[ALLOC_S(_ptr)])

#define ALLOC_OFF_HEAD  8
#define ALLOC_OFF_TOTAL (ALLOC_OFF_HEAD + 1)

/* Allocator increments for ck_realloc_block(). */

#define ALLOC_BLK_INC    256

/* Sanity-checking macros for pointers. */

#define CHECK_PTR(_p) do { \
    if (_p) { \
      if (ALLOC_C1(_p) ^ ALLOC_MAGIC_C1) {\
        if (ALLOC_C1(_p) == ALLOC_MAGIC_F) \
          ABORT("Use after free."); \
        else ABORT("Corrupted head alloc canary."); \
      } \
      if (ALLOC_C2(_p) ^ ALLOC_MAGIC_C2) \
        ABORT("Corrupted tail alloc canary."); \
    } \
  } while (0)

#define CHECK_PTR_EXPR(_p) ({ \
    typeof (_p) _tmp = (_p); \
    CHECK_PTR(_tmp); \
    _tmp; \
  })


/* Allocate a buffer, explicitly not zeroing it. Returns NULL for zero-sized
   requests. */

static inline void* DFL_ck_alloc_nozero(u32 size) {

  void* ret;

  if (!size) return NULL;

  ALLOC_CHECK_SIZE(size);
  ret = malloc(size + ALLOC_OFF_TOTAL);
  ALLOC_CHECK_RESULT(ret, size);

  ret += ALLOC_OFF_HEAD;

  ALLOC_C1(ret) = ALLOC_MAGIC_C1;
  ALLOC_S(ret)  = size;
  ALLOC_C2(ret) = ALLOC_MAGIC_C2;

  return ret;

}


/* Allocate a buffer, returning zeroed memory. */

static inline void* DFL_ck_alloc(u32 size) {

  void* mem;

  if (!size) return NULL;
  mem = DFL_ck_alloc_nozero(size);

  return memset(mem, 0, size);

}


/* Free memory, checking for double free and corrupted heap. When DEBUG_BUILD
   is set, the old memory will be also clobbered with 0xFF. */

static inline void DFL_ck_free(void* mem) {

  if (!mem) return;

  CHECK_PTR(mem);

#ifdef DEBUG_BUILD

  /* Catch pointer issues sooner. */
  memset(mem, 0xFF, ALLOC_S(mem));

#endif /* DEBUG_BUILD */

  ALLOC_C1(mem) = ALLOC_MAGIC_F;

  free(mem - ALLOC_OFF_HEAD);

}


/* Re-allocate a buffer, checking for issues and zeroing any newly-added tail.
   With DEBUG_BUILD, the buffer is always reallocated to a new addresses and the
   old memory is clobbered with 0xFF. */

static inline void* DFL_ck_realloc(void* orig, u32 size) {

  void* ret;
  u32   old_size = 0;

  if (!size) {

    DFL_ck_free(orig);
    return NULL;

  }

  if (orig) {

    CHECK_PTR(orig);

#ifndef DEBUG_BUILD
    ALLOC_C1(orig) = ALLOC_MAGIC_F;
#endif /* !DEBUG_BUILD */

    old_size  = ALLOC_S(orig);
    orig     -= ALLOC_OFF_HEAD;

    ALLOC_CHECK_SIZE(old_size);

  }

  ALLOC_CHECK_SIZE(size);

#ifndef DEBUG_BUILD

  ret = realloc(orig, size + ALLOC_OFF_TOTAL);
  ALLOC_CHECK_RESULT(ret, size);

#else

  /* Catch pointer issues sooner: force relocation and make sure that the
     original buffer is wiped. */

  ret = malloc(size + ALLOC_OFF_TOTAL);
  ALLOC_CHECK_RESULT(ret, size);

  if (orig) {

    memcpy(ret + ALLOC_OFF_HEAD, orig + ALLOC_OFF_HEAD, MIN(size, old_size));
    memset(orig + ALLOC_OFF_HEAD, 0xFF, old_size);

    ALLOC_C1(orig + ALLOC_OFF_HEAD) = ALLOC_MAGIC_F;

    free(orig);

  }

#endif /* ^!DEBUG_BUILD */

  ret += ALLOC_OFF_HEAD;

  ALLOC_C1(ret) = ALLOC_MAGIC_C1;
  ALLOC_S(ret)  = size;
  ALLOC_C2(ret) = ALLOC_MAGIC_C2;

  if (size > old_size)
    memset(ret + old_size, 0, size - old_size);

  return ret;

}


/* Re-allocate a buffer with ALLOC_BLK_INC increments (used to speed up
   repeated small reallocs without complicating the user code). */

static inline void* DFL_ck_realloc_block(void* orig, u32 size) {

#ifndef DEBUG_BUILD

  if (orig) {

    CHECK_PTR(orig);

    if (ALLOC_S(orig) >= size) return orig;

    size += ALLOC_BLK_INC;

  }

#endif /* !DEBUG_BUILD */

  return DFL_ck_realloc(orig, size);

}


/* Create a buffer with a copy of a string. Returns NULL for NULL inputs. */

static inline u8* DFL_ck_strdup(u8* str) {

  void* ret;
  u32   size;

  if (!str) return NULL;

  size = strlen((char*)str) + 1;

  ALLOC_CHECK_SIZE(size);
  ret = malloc(size + ALLOC_OFF_TOTAL);
  ALLOC_CHECK_RESULT(ret, size);

  ret += ALLOC_OFF_HEAD;

  ALLOC_C1(ret) = ALLOC_MAGIC_C1;
  ALLOC_S(ret)  = size;
  ALLOC_C2(ret) = ALLOC_MAGIC_C2;

  return memcpy(ret, str, size);

}


/* Create a buffer with a copy of a memory block. Returns NULL for zero-sized
   or NULL inputs. */

static inline void* DFL_ck_memdup(void* mem, u32 size) {

  void* ret;

  if (!mem || !size) return NULL;

  ALLOC_CHECK_SIZE(size);
  ret = malloc(size + ALLOC_OFF_TOTAL);
  ALLOC_CHECK_RESULT(ret, size);
  
  ret += ALLOC_OFF_HEAD;

  ALLOC_C1(ret) = ALLOC_MAGIC_C1;
  ALLOC_S(ret)  = size;
  ALLOC_C2(ret) = ALLOC_MAGIC_C2;

  return memcpy(ret, mem, size);

}


/* Create a buffer with a block of text, appending a NUL terminator at the end.
   Returns NULL for zero-sized or NULL inputs. */

static inline u8* DFL_ck_memdup_str(u8* mem, u32 size) {

  u8* ret;

  if (!mem || !size) return NULL;

  ALLOC_CHECK_SIZE(size);
  ret = malloc(size + ALLOC_OFF_TOTAL + 1);
  ALLOC_CHECK_RESULT(ret, size);
  
  ret += ALLOC_OFF_HEAD;

  ALLOC_C1(ret) = ALLOC_MAGIC_C1;
  ALLOC_S(ret)  = size;
  ALLOC_C2(ret) = ALLOC_MAGIC_C2;

  memcpy(ret, mem, size);
  ret[size] = 0;

  return ret;

}


#ifndef DEBUG_BUILD

/* In non-debug mode, we just do straightforward aliasing of the above functions
   to user-visible names such as ck_alloc(). */

#define ck_alloc          DFL_ck_alloc
#define ck_alloc_nozero   DFL_ck_alloc_nozero
#define ck_realloc        DFL_ck_realloc
#define ck_realloc_block  DFL_ck_realloc_block
#define ck_strdup         DFL_ck_strdup
#define ck_memdup         DFL_ck_memdup
#define ck_memdup_str     DFL_ck_memdup_str
#define ck_free           DFL_ck_free

#define alloc_report()

#else

/* In debugging mode, we also track allocations to detect memory leaks, and the
   flow goes through one more layer of indirection. */

/* Alloc tracking data structures: */

#define ALLOC_BUCKETS     4096

struct TRK_obj {
  void *ptr;
  char *file, *func;
  u32  line;
};

#ifdef AFL_MAIN

struct TRK_obj* TRK[ALLOC_BUCKETS];
u32 TRK_cnt[ALLOC_BUCKETS];

#  define alloc_report() TRK_report()

#else

extern struct TRK_obj* TRK[ALLOC_BUCKETS];
extern u32 TRK_cnt[ALLOC_BUCKETS];

#  define alloc_report()

#endif /* ^AFL_MAIN */

/* Bucket-assigning function for a given pointer: */

#define TRKH(_ptr) (((((u32)(_ptr)) >> 16) ^ ((u32)(_ptr))) % ALLOC_BUCKETS)


/* Add a new entry to the list of allocated objects. */

static inline void TRK_alloc_buf(void* ptr, const char* file, const char* func,
                                 u32 line) {

  u32 i, bucket;

  if (!ptr) return;

  bucket = TRKH(ptr);

  /* Find a free slot in the list of entries for that bucket. */

  for (i = 0; i < TRK_cnt[bucket]; i++)

    if (!TRK[bucket][i].ptr) {

      TRK[bucket][i].ptr  = ptr;
      TRK[bucket][i].file = (char*)file;
      TRK[bucket][i].func = (char*)func;
      TRK[bucket][i].line = line;
      return;

    }

  /* No space available - allocate more. */

  TRK[bucket] = DFL_ck_realloc_block(TRK[bucket],
    (TRK_cnt[bucket] + 1) * sizeof(struct TRK_obj));

  TRK[bucket][i].ptr  = ptr;
  TRK[bucket][i].file = (char*)file;
  TRK[bucket][i].func = (char*)func;
  TRK[bucket][i].line = line;

  TRK_cnt[bucket]++;

}


/* Remove entry from the list of allocated objects. */

static inline void TRK_free_buf(void* ptr, const char* file, const char* func,
                                u32 line) {

  u32 i, bucket;

  if (!ptr) return;

  bucket = TRKH(ptr);

  /* Find the element on the list... */

  for (i = 0; i < TRK_cnt[bucket]; i++)

    if (TRK[bucket][i].ptr == ptr) {

      TRK[bucket][i].ptr = 0;
      return;

    }

  WARNF("ALLOC: Attempt to free non-allocated memory in %s (%s:%u)",
        func, file, line);

}


/* Do a final report on all non-deallocated objects. */

static inline void TRK_report(void) {

  u32 i, bucket;

  fflush(0);

  for (bucket = 0; bucket < ALLOC_BUCKETS; bucket++)
    for (i = 0; i < TRK_cnt[bucket]; i++)
      if (TRK[bucket][i].ptr)
        WARNF("ALLOC: Memory never freed, created in %s (%s:%u)",
              TRK[bucket][i].func, TRK[bucket][i].file, TRK[bucket][i].line);

}


/* Simple wrappers for non-debugging functions: */

static inline void* TRK_ck_alloc(u32 size, const char* file, const char* func,
                                 u32 line) {

  void* ret = DFL_ck_alloc(size);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void* TRK_ck_realloc(void* orig, u32 size, const char* file,
                                   const char* func, u32 line) {

  void* ret = DFL_ck_realloc(orig, size);
  TRK_free_buf(orig, file, func, line);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void* TRK_ck_realloc_block(void* orig, u32 size, const char* file,
                                         const char* func, u32 line) {

  void* ret = DFL_ck_realloc_block(orig, size);
  TRK_free_buf(orig, file, func, line);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void* TRK_ck_strdup(u8* str, const char* file, const char* func,
                                  u32 line) {

  void* ret = DFL_ck_strdup(str);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void* TRK_ck_memdup(void* mem, u32 size, const char* file,
                                  const char* func, u32 line) {

  void* ret = DFL_ck_memdup(mem, size);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void* TRK_ck_memdup_str(void* mem, u32 size, const char* file,
                                      const char* func, u32 line) {

  void* ret = DFL_ck_memdup_str(mem, size);
  TRK_alloc_buf(ret, file, func, line);
  return ret;

}


static inline void TRK_ck_free(void* ptr, const char* file,
                                const char* func, u32 line) {

  TRK_free_buf(ptr, file, func, line);
  DFL_ck_free(ptr);

}

/* Aliasing user-facing names to tracking functions: */

#define ck_alloc(_p1) \
  TRK_ck_alloc(_p1, __FILE__, __FUNCTION__, __LINE__)

#define ck_alloc_nozero(_p1) \
  TRK_ck_alloc(_p1, __FILE__, __FUNCTION__, __LINE__)

#define ck_realloc(_p1, _p2) \
  TRK_ck_realloc(_p1, _p2, __FILE__, __FUNCTION__, __LINE__)

#define ck_realloc_block(_p1, _p2) \
  TRK_ck_realloc_block(_p1, _p2, __FILE__, __FUNCTION__, __LINE__)

#define ck_strdup(_p1) \
  TRK_ck_strdup(_p1, __FILE__, __FUNCTION__, __LINE__)

#define ck_memdup(_p1, _p2) \
  TRK_ck_memdup(_p1, _p2, __FILE__, __FUNCTION__, __LINE__)

#define ck_memdup_str(_p1, _p2) \
  TRK_ck_memdup_str(_p1, _p2, __FILE__, __FUNCTION__, __LINE__)

#define ck_free(_p1) \
  TRK_ck_free(_p1, __FILE__, __FUNCTION__, __LINE__)

#endif /* ^!DEBUG_BUILD */

#endif /* ! _HAVE_ALLOC_INL_H */