1 
2 /* pngmem.c - stub functions for memory allocation
3  *
4  * Last changed in libpng 1.6.8 [December 19, 2013]
5  * Copyright (c) 1998-2013 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 */
24 void /* PRIVATE */
png_destroy_png_struct(png_structrp png_ptr)25 png_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 then 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  */
49 PNG_FUNCTION(png_voidp,PNGAPI
50 png_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  */
67 PNG_FUNCTION(png_voidp /* PRIVATE */,
68 png_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    if (size > 0 && size <= PNG_SIZE_MAX
81 #     ifdef PNG_MAX_MALLOC_64K
82          && size <= 65536U
83 #     endif
84       )
85    {
86 #ifdef PNG_USER_MEM_SUPPORTED
87       if (png_ptr != NULL && png_ptr->malloc_fn != NULL)
88          return png_ptr->malloc_fn(png_constcast(png_structrp,png_ptr), size);
89 
90       else
91 #endif
92          return malloc((size_t)size); /* checked for truncation above */
93    }
94 
95    else
96       return NULL;
97 }
98 
99 #if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\
100    defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)
101 /* This is really here only to work round a spurious warning in GCC 4.6 and 4.7
102  * that arises because of the checks in png_realloc_array that are repeated in
103  * png_malloc_array.
104  */
105 static png_voidp
png_malloc_array_checked(png_const_structrp png_ptr,int nelements,size_t element_size)106 png_malloc_array_checked(png_const_structrp png_ptr, int nelements,
107    size_t element_size)
108 {
109    png_alloc_size_t req = nelements; /* known to be > 0 */
110 
111    if (req <= PNG_SIZE_MAX/element_size)
112       return png_malloc_base(png_ptr, req * element_size);
113 
114    /* The failure case when the request is too large */
115    return NULL;
116 }
117 
118 PNG_FUNCTION(png_voidp /* PRIVATE */,
119 png_malloc_array,(png_const_structrp png_ptr, int nelements,
120    size_t element_size),PNG_ALLOCATED)
121 {
122    if (nelements <= 0 || element_size == 0)
123       png_error(png_ptr, "internal error: array alloc");
124 
125    return png_malloc_array_checked(png_ptr, nelements, element_size);
126 }
127 
128 PNG_FUNCTION(png_voidp /* PRIVATE */,
129 png_realloc_array,(png_const_structrp png_ptr, png_const_voidp old_array,
130    int old_elements, int add_elements, size_t element_size),PNG_ALLOCATED)
131 {
132    /* These are internal errors: */
133    if (add_elements <= 0 || element_size == 0 || old_elements < 0 ||
134       (old_array == NULL && old_elements > 0))
135       png_error(png_ptr, "internal error: array realloc");
136 
137    /* Check for overflow on the elements count (so the caller does not have to
138     * check.)
139     */
140    if (add_elements <= INT_MAX - old_elements)
141    {
142       png_voidp new_array = png_malloc_array_checked(png_ptr,
143          old_elements+add_elements, element_size);
144 
145       if (new_array != NULL)
146       {
147          /* Because png_malloc_array worked the size calculations below cannot
148           * overflow.
149           */
150          if (old_elements > 0)
151             memcpy(new_array, old_array, element_size*(unsigned)old_elements);
152 
153          memset((char*)new_array + element_size*(unsigned)old_elements, 0,
154             element_size*(unsigned)add_elements);
155 
156          return new_array;
157       }
158    }
159 
160    return NULL; /* error */
161 }
162 #endif /* TEXT || sPLT || STORE_UNKNOWN_CHUNKS */
163 
164 /* Various functions that have different error handling are derived from this.
165  * png_malloc always exists, but if PNG_USER_MEM_SUPPORTED is defined a separate
166  * function png_malloc_default is also provided.
167  */
168 PNG_FUNCTION(png_voidp,PNGAPI
169 png_malloc,(png_const_structrp png_ptr, png_alloc_size_t size),PNG_ALLOCATED)
170 {
171    png_voidp ret;
172 
173    if (png_ptr == NULL)
174       return NULL;
175 
176    ret = png_malloc_base(png_ptr, size);
177 
178    if (ret == NULL)
179        png_error(png_ptr, "Out of memory"); /* 'm' means png_malloc */
180 
181    return ret;
182 }
183 
184 #ifdef PNG_USER_MEM_SUPPORTED
185 PNG_FUNCTION(png_voidp,PNGAPI
186 png_malloc_default,(png_const_structrp png_ptr, png_alloc_size_t size),
187    PNG_ALLOCATED PNG_DEPRECATED)
188 {
189    png_voidp ret;
190 
191    if (png_ptr == NULL)
192       return NULL;
193 
194    /* Passing 'NULL' here bypasses the application provided memory handler. */
195    ret = png_malloc_base(NULL/*use malloc*/, size);
196 
197    if (ret == NULL)
198       png_error(png_ptr, "Out of Memory"); /* 'M' means png_malloc_default */
199 
200    return ret;
201 }
202 #endif /* PNG_USER_MEM_SUPPORTED */
203 
204 /* This function was added at libpng version 1.2.3.  The png_malloc_warn()
205  * function will issue a png_warning and return NULL instead of issuing a
206  * png_error, if it fails to allocate the requested memory.
207  */
208 PNG_FUNCTION(png_voidp,PNGAPI
209 png_malloc_warn,(png_const_structrp png_ptr, png_alloc_size_t size),
210    PNG_ALLOCATED)
211 {
212    if (png_ptr != NULL)
213    {
214       png_voidp ret = png_malloc_base(png_ptr, size);
215 
216       if (ret != NULL)
217          return ret;
218 
219       png_warning(png_ptr, "Out of memory");
220    }
221 
222    return NULL;
223 }
224 
225 /* Free a pointer allocated by png_malloc().  If ptr is NULL, return
226  * without taking any action.
227  */
228 void PNGAPI
png_free(png_const_structrp png_ptr,png_voidp ptr)229 png_free(png_const_structrp png_ptr, png_voidp ptr)
230 {
231    if (png_ptr == NULL || ptr == NULL)
232       return;
233 
234 #ifdef PNG_USER_MEM_SUPPORTED
235    if (png_ptr->free_fn != NULL)
236       png_ptr->free_fn(png_constcast(png_structrp,png_ptr), ptr);
237 
238    else
239       png_free_default(png_ptr, ptr);
240 }
241 
242 PNG_FUNCTION(void,PNGAPI
243 png_free_default,(png_const_structrp png_ptr, png_voidp ptr),PNG_DEPRECATED)
244 {
245    if (png_ptr == NULL || ptr == NULL)
246       return;
247 #endif /* PNG_USER_MEM_SUPPORTED */
248 
249    free(ptr);
250 }
251 
252 #ifdef PNG_USER_MEM_SUPPORTED
253 /* This function is called when the application wants to use another method
254  * of allocating and freeing memory.
255  */
256 void PNGAPI
png_set_mem_fn(png_structrp png_ptr,png_voidp mem_ptr,png_malloc_ptr malloc_fn,png_free_ptr free_fn)257 png_set_mem_fn(png_structrp png_ptr, png_voidp mem_ptr, png_malloc_ptr
258   malloc_fn, png_free_ptr free_fn)
259 {
260    if (png_ptr != NULL)
261    {
262       png_ptr->mem_ptr = mem_ptr;
263       png_ptr->malloc_fn = malloc_fn;
264       png_ptr->free_fn = free_fn;
265    }
266 }
267 
268 /* This function returns a pointer to the mem_ptr associated with the user
269  * functions.  The application should free any memory associated with this
270  * pointer before png_write_destroy and png_read_destroy are called.
271  */
272 png_voidp PNGAPI
png_get_mem_ptr(png_const_structrp png_ptr)273 png_get_mem_ptr(png_const_structrp png_ptr)
274 {
275    if (png_ptr == NULL)
276       return NULL;
277 
278    return png_ptr->mem_ptr;
279 }
280 #endif /* PNG_USER_MEM_SUPPORTED */
281 #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */
282