1/*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.  Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25/*    $OpenBSD: reallocarray.c,v 1.1 2014/05/08 21:43:49 deraadt Exp $    */
26/*
27 * Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
28 *
29 * Permission to use, copy, modify, and distribute this software for any
30 * purpose with or without fee is hereby granted, provided that the above
31 * copyright notice and this permission notice appear in all copies.
32 *
33 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
34 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
35 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
36 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
37 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
38 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
39 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
40 */
41
42#include <sys/types.h>
43#include <errno.h>
44#include <stdint.h>
45#include <stdlib.h>
46
47/*
48 * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
49 * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
50 */
51#define MUL_NO_OVERFLOW    ((size_t)1 << (sizeof(size_t) * 4))
52
53void *
54reallocarray(void *optr, size_t nmemb, size_t size)
55{
56    if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
57        nmemb > 0 && SIZE_MAX / nmemb < size) {
58        errno = ENOMEM;
59        return NULL;
60    }
61    /*
62     * Head off variations in realloc behavior on different
63     * platforms (reported by MarkR <mrogers6@users.sf.net>)
64     *
65     * The behaviour of reallocarray is implementation-defined if
66     * nmemb or size is zero. It can return NULL or non-NULL
67     * depending on the platform.
68     * https://www.securecoding.cert.org/confluence/display/c/MEM04-C.Beware+of+zero-lengthallocations
69     *
70     * Here are some extracts from realloc man pages on different platforms.
71     *
72     * void realloc( void memblock, size_t size );
73     *
74     * Windows:
75     *
76     * If there is not enough available memory to expand the block
77     * to the given size, the original block is left unchanged,
78     * and NULL is returned.  If size is zero, then the block
79     * pointed to by memblock is freed; the return value is NULL,
80     * and memblock is left pointing at a freed block.
81     *
82     * OpenBSD:
83     *
84     * If size or nmemb is equal to 0, a unique pointer to an
85     * access protected, zero sized object is returned. Access via
86     * this pointer will generate a SIGSEGV exception.
87     *
88     * Linux:
89     *
90     * If size was equal to 0, either NULL or a pointer suitable
91     * to be passed to free() is returned.
92     *
93     * OS X:
94     *
95     * If size is zero and ptr is not NULL, a new, minimum sized
96     * object is allocated and the original object is freed.
97     *
98     * It looks like images with zero width or height can trigger
99     * this, and fuzzing behaviour will differ by platform, so
100     * fuzzing on one platform may not detect zero-size allocation
101     * problems on other platforms.
102     */
103    if (size == 0 || nmemb == 0)
104        return NULL;
105    return realloc(optr, size * nmemb);
106}
107