1
  2/* pngmem.c - stub functions for memory allocation
  3 *
  4 * Last changed in libpng 1.6.26 [October 20, 2016]
  5 * Copyright (c) 1998-2002,2004,2006-2014,2016 Glenn Randers-Pehrson
  6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  8 *
  9 * This code is released under the libpng license.
 10 * For conditions of distribution and use, see the disclaimer
 11 * and license in png.h
 12 *
 13 * This file provides a location for all memory allocation.  Users who
 14 * need special memory handling are expected to supply replacement
 15 * functions for png_malloc() and png_free(), and to use
 16 * png_create_read_struct_2() and png_create_write_struct_2() to
 17 * identify the replacement functions.
 18 */
 19
 20#include "pngpriv.h"
 21
 22#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
 23/* Free a png_struct */
 24void /* PRIVATE */
 25png_destroy_png_struct(png_structrp png_ptr)
 26{
 27   if (png_ptr != NULL)
 28   {
 29      /* png_free might call png_error and may certainly call
 30       * png_get_mem_ptr, so fake a temporary png_struct to support this.
 31       */
 32      png_struct dummy_struct = *png_ptr;
 33      memset(png_ptr, 0, (sizeof *png_ptr));
 34      png_free(&dummy_struct, png_ptr);
 35
 36#     ifdef PNG_SETJMP_SUPPORTED
 37         /* We may have a jmp_buf left to deallocate. */
 38         png_free_jmpbuf(&dummy_struct);
 39#     endif
 40   }
 41}
 42
 43/* Allocate memory.  For reasonable files, size should never exceed
 44 * 64K.  However, zlib may allocate more than 64K if you don't tell
 45 * it not to.  See zconf.h and png.h for more information.  zlib does
 46 * need to allocate exactly 64K, so whatever you call here must
 47 * have the ability to do that.
 48 */
 49PNG_FUNCTION(png_voidp,PNGAPI
 50png_calloc,(png_const_structrp png_ptr, png_alloc_size_t size),PNG_ALLOCATED)
 51{
 52   png_voidp ret;
 53
 54   ret = png_malloc(png_ptr, size);
 55
 56   if (ret != NULL)
 57      memset(ret, 0, size);
 58
 59   return ret;
 60}
 61
 62/* png_malloc_base, an internal function added at libpng 1.6.0, does the work of
 63 * allocating memory, taking into account limits and PNG_USER_MEM_SUPPORTED.
 64 * Checking and error handling must happen outside this routine; it returns NULL
 65 * if the allocation cannot be done (for any reason.)
 66 */
 67PNG_FUNCTION(png_voidp /* PRIVATE */,
 68png_malloc_base,(png_const_structrp png_ptr, png_alloc_size_t size),
 69    PNG_ALLOCATED)
 70{
 71   /* Moved to png_malloc_base from png_malloc_default in 1.6.0; the DOS
 72    * allocators have also been removed in 1.6.0, so any 16-bit system now has
 73    * to implement a user memory handler.  This checks to be sure it isn't
 74    * called with big numbers.
 75    */
 76#ifndef PNG_USER_MEM_SUPPORTED
 77   PNG_UNUSED(png_ptr)
 78#endif
 79
 80   /* Some compilers complain that this is always true.  However, it
 81    * can be false when integer overflow happens.
 82    */
 83   if (size > 0 && size <= PNG_SIZE_MAX
 84#     ifdef PNG_MAX_MALLOC_64K
 85         && size <= 65536U
 86#     endif
 87      )
 88   {
 89#ifdef PNG_USER_MEM_SUPPORTED
 90      if (png_ptr != NULL && png_ptr->malloc_fn != NULL)
 91         return png_ptr->malloc_fn(png_constcast(png_structrp,png_ptr), size);
 92
 93      else
 94#endif
 95         return malloc((size_t)size); /* checked for truncation above */
 96   }
 97
 98   else
 99      return NULL;
100}
101
102#if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\
103   defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)
104/* This is really here only to work round a spurious warning in GCC 4.6 and 4.7
105 * that arises because of the checks in png_realloc_array that are repeated in
106 * png_malloc_array.
107 */
108static png_voidp
109png_malloc_array_checked(png_const_structrp png_ptr, int nelements,
110    size_t element_size)
111{
112   png_alloc_size_t req = (png_alloc_size_t)nelements; /* known to be > 0 */
113
114   if (req <= PNG_SIZE_MAX/element_size)
115      return png_malloc_base(png_ptr, req * element_size);
116
117   /* The failure case when the request is too large */
118   return NULL;
119}
120
121PNG_FUNCTION(png_voidp /* PRIVATE */,
122png_malloc_array,(png_const_structrp png_ptr, int nelements,
123    size_t element_size),PNG_ALLOCATED)
124{
125   if (nelements <= 0 || element_size == 0)
126      png_error(png_ptr, "internal error: array alloc");
127
128   return png_malloc_array_checked(png_ptr, nelements, element_size);
129}
130
131PNG_FUNCTION(png_voidp /* PRIVATE */,
132png_realloc_array,(png_const_structrp png_ptr, png_const_voidp old_array,
133    int old_elements, int add_elements, size_t element_size),PNG_ALLOCATED)
134{
135   /* These are internal errors: */
136   if (add_elements <= 0 || element_size == 0 || old_elements < 0 ||
137      (old_array == NULL && old_elements > 0))
138      png_error(png_ptr, "internal error: array realloc");
139
140   /* Check for overflow on the elements count (so the caller does not have to
141    * check.)
142    */
143   if (add_elements <= INT_MAX - old_elements)
144   {
145      png_voidp new_array = png_malloc_array_checked(png_ptr,
146          old_elements+add_elements, element_size);
147
148      if (new_array != NULL)
149      {
150         /* Because png_malloc_array worked the size calculations below cannot
151          * overflow.
152          */
153         if (old_elements > 0)
154            memcpy(new_array, old_array, element_size*(unsigned)old_elements);
155
156         memset((char*)new_array + element_size*(unsigned)old_elements, 0,
157             element_size*(unsigned)add_elements);
158
159         return new_array;
160      }
161   }
162
163   return NULL; /* error */
164}
165#endif /* TEXT || sPLT || STORE_UNKNOWN_CHUNKS */
166
167/* Various functions that have different error handling are derived from this.
168 * png_malloc always exists, but if PNG_USER_MEM_SUPPORTED is defined a separate
169 * function png_malloc_default is also provided.
170 */
171PNG_FUNCTION(png_voidp,PNGAPI
172png_malloc,(png_const_structrp png_ptr, png_alloc_size_t size),PNG_ALLOCATED)
173{
174   png_voidp ret;
175
176   if (png_ptr == NULL)
177      return NULL;
178
179   ret = png_malloc_base(png_ptr, size);
180
181   if (ret == NULL)
182       png_error(png_ptr, "Out of memory"); /* 'm' means png_malloc */
183
184   return ret;
185}
186
187#ifdef PNG_USER_MEM_SUPPORTED
188PNG_FUNCTION(png_voidp,PNGAPI
189png_malloc_default,(png_const_structrp png_ptr, png_alloc_size_t size),
190    PNG_ALLOCATED PNG_DEPRECATED)
191{
192   png_voidp ret;
193
194   if (png_ptr == NULL)
195      return NULL;
196
197   /* Passing 'NULL' here bypasses the application provided memory handler. */
198   ret = png_malloc_base(NULL/*use malloc*/, size);
199
200   if (ret == NULL)
201      png_error(png_ptr, "Out of Memory"); /* 'M' means png_malloc_default */
202
203   return ret;
204}
205#endif /* USER_MEM */
206
207/* This function was added at libpng version 1.2.3.  The png_malloc_warn()
208 * function will issue a png_warning and return NULL instead of issuing a
209 * png_error, if it fails to allocate the requested memory.
210 */
211PNG_FUNCTION(png_voidp,PNGAPI
212png_malloc_warn,(png_const_structrp png_ptr, png_alloc_size_t size),
213    PNG_ALLOCATED)
214{
215   if (png_ptr != NULL)
216   {
217      png_voidp ret = png_malloc_base(png_ptr, size);
218
219      if (ret != NULL)
220         return ret;
221
222      png_warning(png_ptr, "Out of memory");
223   }
224
225   return NULL;
226}
227
228/* Free a pointer allocated by png_malloc().  If ptr is NULL, return
229 * without taking any action.
230 */
231void PNGAPI
232png_free(png_const_structrp png_ptr, png_voidp ptr)
233{
234   if (png_ptr == NULL || ptr == NULL)
235      return;
236
237#ifdef PNG_USER_MEM_SUPPORTED
238   if (png_ptr->free_fn != NULL)
239      png_ptr->free_fn(png_constcast(png_structrp,png_ptr), ptr);
240
241   else
242      png_free_default(png_ptr, ptr);
243}
244
245PNG_FUNCTION(void,PNGAPI
246png_free_default,(png_const_structrp png_ptr, png_voidp ptr),PNG_DEPRECATED)
247{
248   if (png_ptr == NULL || ptr == NULL)
249      return;
250#endif /* USER_MEM */
251
252   free(ptr);
253}
254
255#ifdef PNG_USER_MEM_SUPPORTED
256/* This function is called when the application wants to use another method
257 * of allocating and freeing memory.
258 */
259void PNGAPI
260png_set_mem_fn(png_structrp png_ptr, png_voidp mem_ptr, png_malloc_ptr
261  malloc_fn, png_free_ptr free_fn)
262{
263   if (png_ptr != NULL)
264   {
265      png_ptr->mem_ptr = mem_ptr;
266      png_ptr->malloc_fn = malloc_fn;
267      png_ptr->free_fn = free_fn;
268   }
269}
270
271/* This function returns a pointer to the mem_ptr associated with the user
272 * functions.  The application should free any memory associated with this
273 * pointer before png_write_destroy and png_read_destroy are called.
274 */
275png_voidp PNGAPI
276png_get_mem_ptr(png_const_structrp png_ptr)
277{
278   if (png_ptr == NULL)
279      return NULL;
280
281   return png_ptr->mem_ptr;
282}
283#endif /* USER_MEM */
284#endif /* READ || WRITE */