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/* $OpenBSD: reallocarray.c,v 1.1 2014/05/08 21:43:49 deraadt Exp $ */
/*
* Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#ifndef SIZE_MAX
#define SIZE_MAX UINTPTR_MAX
#endif
/*
* This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
* if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
*/
#define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
void *
openbsd_reallocarray(void *optr, size_t nmemb, size_t size)
{
if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
nmemb > 0 && SIZE_MAX / nmemb < size) {
errno = ENOMEM;
return NULL;
}
/*
* Head off variations in realloc behavior on different
* platforms (reported by MarkR <mrogers6@users.sf.net>)
*
* The behaviour of reallocarray is implementation-defined if
* nmemb or size is zero. It can return NULL or non-NULL
* depending on the platform.
* https://www.securecoding.cert.org/confluence/display/c/MEM04-C.Beware+of+zero-lengthallocations
*
* Here are some extracts from realloc man pages on different platforms.
*
* void realloc( void memblock, size_t size );
*
* Windows:
*
* If there is not enough available memory to expand the block
* to the given size, the original block is left unchanged,
* and NULL is returned. If size is zero, then the block
* pointed to by memblock is freed; the return value is NULL,
* and memblock is left pointing at a freed block.
*
* OpenBSD:
*
* If size or nmemb is equal to 0, a unique pointer to an
* access protected, zero sized object is returned. Access via
* this pointer will generate a SIGSEGV exception.
*
* Linux:
*
* If size was equal to 0, either NULL or a pointer suitable
* to be passed to free() is returned.
*
* OS X:
*
* If size is zero and ptr is not NULL, a new, minimum sized
* object is allocated and the original object is freed.
*
* It looks like images with zero width or height can trigger
* this, and fuzzing behaviour will differ by platform, so
* fuzzing on one platform may not detect zero-size allocation
* problems on other platforms.
*/
if (size == 0 || nmemb == 0)
return NULL;
return realloc(optr, size * nmemb);
}
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