Replace our buggy recallocarray implementation one with the portable one

from OpenBSD.

crypto/external/bsd/openssh/dist/recallocarray.c

@@ -1,51 +1,91 @@
-/*	$NetBSD: recallocarray.c,v 1.1 2017/10/07 21:14:59 christos Exp $	*/
-/*	$OpenBSD: reallocarray.c,v 1.1 2014/05/08 21:43:49 deraadt Exp $	*/
+/*	$OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $	*/
 
-/*-
- * Copyright (c) 2015 The NetBSD Foundation, Inc.
- * All rights reserved.
+/*
+ * Copyright (c) 2008, 2017 Otto Moerbeek <otto@drijf.net>
  *
- * This code is derived from software contributed to The NetBSD Foundation
- * by Christos Zoulas.
+ * 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.
  *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
- * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
- * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
+ * 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.
  */
 
+/* OPENBSD ORIGINAL: lib/libc/stdlib/recallocarray.c */
+
 #include "includes.h"
-#include <sys/cdefs.h>
-__RCSID("$NetBSD: recallocarray.c,v 1.1 2017/10/07 21:14:59 christos Exp $");
+#ifndef HAVE_RECALLOCARRAY
 
 #include <errno.h>
-#include <string.h>
 #include <stdlib.h>
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <string.h>
+#include <unistd.h>
+
+/*
+ * 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 *
-recallocarray(void *optr, size_t omemb, size_t nmemb, size_t size)
+recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
 {
-	char *nptr = reallocarray(optr, nmemb, size);
+	size_t oldsize, newsize;
+	void *newptr;
 
-	if (nptr == NULL || omemb >= nmemb)
-		return nptr;
+	if (ptr == NULL)
+		return calloc(newnmemb, size);
 
-	memset(nptr + omemb * size, 0, (nmemb - omemb) * size);
-	return nptr;
+	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
+		errno = ENOMEM;
+		return NULL;
+	}
+	newsize = newnmemb * size;
+
+	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
+	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
+		errno = EINVAL;
+		return NULL;
+	}
+	oldsize = oldnmemb * size;
+	
+	/*
+	 * Don't bother too much if we're shrinking just a bit,
+	 * we do not shrink for series of small steps, oh well.
+	 */
+	if (newsize <= oldsize) {
+		size_t d = oldsize - newsize;
+
+		if (d < oldsize / 2 && d < (size_t)getpagesize()) {
+			memset((char *)ptr + newsize, 0, d);
+			return ptr;
+		}
+	}
+
+	newptr = malloc(newsize);
+	if (newptr == NULL)
+		return NULL;
+
+	if (newsize > oldsize) {
+		memcpy(newptr, ptr, oldsize);
+		memset((char *)newptr + oldsize, 0, newsize - oldsize);
+	} else
+		memcpy(newptr, ptr, newsize);
+
+	explicit_bzero(ptr, oldsize);
+	free(ptr);
+
+	return newptr;
 }
+/* DEF_WEAK(recallocarray); */
+
+#endif /* HAVE_RECALLOCARRAY */