diff --git a/lib/libc/stdlib/reallocarray.c b/lib/libc/stdlib/reallocarray.c
index 0868804486cc..3632734c84de 100644
--- a/lib/libc/stdlib/reallocarray.c
+++ b/lib/libc/stdlib/reallocarray.c
@@ -1,39 +1,35 @@
 /*	$OpenBSD: reallocarray.c,v 1.2 2014/12/08 03:45:00 bcook 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 <stdckdint.h>
 #include <stdint.h>
 #include <stdlib.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 *
 reallocarray(void *optr, size_t nmemb, size_t size)
 {
+	size_t nbytes;
 
-	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
-	    nmemb > 0 && SIZE_MAX / nmemb < size) {
+	if (ckd_mul(&nbytes, nmemb, size)) {
 		errno = ENOMEM;
 		return (NULL);
 	}
-	return (realloc(optr, size * nmemb));
+
+	return (realloc(optr, nbytes));
 }
diff --git a/lib/libopenbsd/recallocarray.c b/lib/libopenbsd/recallocarray.c
index 11e1fda744c7..cbf1fb2470cf 100644
--- a/lib/libopenbsd/recallocarray.c
+++ b/lib/libopenbsd/recallocarray.c
@@ -1,82 +1,73 @@
 /*	$OpenBSD: recallocarray.c,v 1.1 2017/03/06 18:44:21 otto Exp $	*/
 /*
  * Copyright (c) 2008, 2017 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 <errno.h>
+#include <stdckdint.h>
 #include <stdlib.h>
 #include <stdint.h>
 #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 *, size_t, size_t, size_t);
 
 void *
 recallocarray(void *ptr, size_t oldnmemb, size_t newnmemb, size_t size)
 {
 	size_t oldsize, newsize;
 	void *newptr;
 
 	if (ptr == NULL)
 		return calloc(newnmemb, size);
 
-	if ((newnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
-	    newnmemb > 0 && SIZE_MAX / newnmemb < size) {
+	if (ckd_mul(&newsize, newnmemb, size)) {
 		errno = ENOMEM;
 		return NULL;
 	}
-	newsize = newnmemb * size;
 
-	if ((oldnmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
-	    oldnmemb > 0 && SIZE_MAX / oldnmemb < size) {
+	if (ckd_mul(&oldsize, 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;
 }