3b825735d8
Stateless and I stumbled upon this issue while discussing the semantics of read, accepting a size_t but only being able to return ssize_t, effectively lacking the ability to report successful reads > SSIZE_MAX. The discussion went along and we came to the topic of input-based memory allocations. Basically, it was possible for the argument to a memory-allocation-function to overflow, leading to a segfault later. The OpenBSD-guys came up with the ingenious reallocarray-function, and I implemented it as ereallocarray, which automatically returns on error. Read more about it here[0]. A simple testcase is this (courtesy to stateless): $ sbase-strings -n (2^(32|64) / 4) This will segfault before this patch and properly return an OOM- situation afterwards (thanks to the overflow-check in reallocarray). [0]: http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/calloc.3
52 lines
1.5 KiB
C
52 lines
1.5 KiB
C
/* $OpenBSD: reallocarray.c,v 1.1 2014/05/08 21:43:49 deraadt Exp $ */
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/*
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* Copyright (c) 2008 Otto Moerbeek <otto@drijf.net>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#include <errno.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "../util.h"
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/*
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* This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
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* if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
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*/
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#define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
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void *
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reallocarray(void *optr, size_t nmemb, size_t size)
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{
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if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
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nmemb > 0 && SIZE_MAX / nmemb < size) {
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errno = ENOMEM;
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return NULL;
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}
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return realloc(optr, size * nmemb);
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}
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void *
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ereallocarray(void *optr, size_t nmemb, size_t size)
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{
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void *p;
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if (!(p = reallocarray(optr, nmemb, size)))
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eprintf("reallocarray: out of memory\n");
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return p;
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}
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