Just use sort_reallocarray() everywhere.

usr.bin/sort/file.c

···
-/*	$OpenBSD: file.c,v 1.12 2015/04/01 21:33:01 millert Exp $	*/
+/*	$OpenBSD: file.c,v 1.13 2015/04/01 22:24:02 millert Exp $	*/
 
 /*-
  * Copyright (C) 2009 Gabor Kovesdan <[e-mail]>
···
 			if (remsz > (READ_CHUNK >> 1)) {
 				search_start = fr->cbsz - fr->strbeg;
 				fr->cbsz += READ_CHUNK;
-				fr->buffer = sort_realloc(fr->buffer,
-				    fr->cbsz);
+				fr->buffer = sort_reallocarray(fr->buffer,
+				    1, fr->cbsz);
 				bsz1 = fread(fr->buffer + fr->bsz, 1,
 				    READ_CHUNK, fr->file);
 				if (bsz1 == 0) {

usr.bin/sort/mem.c

···
-/*	$OpenBSD: mem.c,v 1.4 2015/04/01 20:58:13 millert Exp $	*/
+/*	$OpenBSD: mem.c,v 1.5 2015/04/01 22:24:02 millert Exp $	*/
 
 /*-
  * Copyright (C) 2009 Gabor Kovesdan <[e-mail]>
···
 sort_free(void *ptr)
 {
 	free(ptr);
-}
-
-/*
- * realloc() wrapper.
- */
-void *
-sort_realloc(void *ptr, size_t size)
-{
-	if ((ptr = realloc(ptr, size)) == NULL)
-		err(2, NULL);
-	return ptr;
 }
 
 /*

usr.bin/sort/mem.h

···
-/*	$OpenBSD: mem.h,v 1.3 2015/03/30 19:57:36 millert Exp $	*/
+/*	$OpenBSD: mem.h,v 1.4 2015/04/01 22:24:02 millert Exp $	*/
 
 /*-
  * Copyright (C) 2009 Gabor Kovesdan <[e-mail]>
···
 void *sort_calloc(size_t nmemb, size_t size);
 void *sort_malloc(size_t);
 void sort_free(void *ptr);
-void *sort_realloc(void *, size_t);
 void *sort_reallocarray(void *, size_t, size_t);
 char *sort_strdup(const char *);
 int sort_asprintf(char **, const char *, ...);

usr.bin/sort/sort.c

···
-/*	$OpenBSD: sort.c,v 1.66 2015/04/01 21:45:50 millert Exp $	*/
+/*	$OpenBSD: sort.c,v 1.67 2015/04/01 22:24:02 millert Exp $	*/
 
 /*-
  * Copyright (C) 2009 Gabor Kovesdan <[e-mail]>
···
 
 	if (keys_num == 0) {
 		keys_num = 1;
-		keys = sort_realloc(keys, sizeof(struct key_specs));
+		keys = sort_reallocarray(keys, 1, sizeof(struct key_specs));
 		memset(&(keys[0]), 0, sizeof(struct key_specs));
 		keys[0].c1 = 1;
 		keys[0].pos1b = default_sort_mods->bflag;