From 9c54eb6e30459e74a4de37822b497b0b3dc73995 Mon Sep 17 00:00:00 2001
From: Explorer09 <explorer09@gmail.com>
Date: Thu, 19 Jan 2017 16:04:13 +0800
Subject: build: detect overflow for [re]allocate_array.

Use reallocarray() when we have it (i.e. in OpenBSD system). When we
don't, use equivalent overflow detection for our allocate_array and
reallocate_array functions.

Remove lib/reallocarray.c from our LIBOBJS as we no longer need it.

Provide a fallback SIZE_MAX macro definition in flexint.h (not
preprocessor friendly, but enough for our reallocate_array use case).
---
 configure.ac       |  2 +-
 lib/reallocarray.c | 49 -------------------------------------------------
 src/flexint.h      |  4 ++++
 src/misc.c         | 22 ++++++++++++++++------
 4 files changed, 21 insertions(+), 56 deletions(-)
 delete mode 100644 lib/reallocarray.c

diff --git a/configure.ac b/configure.ac
index 1543de0..c6c5bd4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -157,7 +157,7 @@ strchr dnl
 strdup dnl
 strtol)
 
-AC_REPLACE_FUNCS(reallocarray)
+AC_CHECK_FUNCS(reallocarray)
 
 AC_CONFIG_FILES(
 Makefile
diff --git a/lib/reallocarray.c b/lib/reallocarray.c
deleted file mode 100644
index 0c1e250..0000000
--- a/lib/reallocarray.c
+++ /dev/null
@@ -1,49 +0,0 @@
-/*	$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.
- */
-
-/* OPENBSD ORIGINAL: lib/libc/stdlib/reallocarray.c */
-
-#include <config.h>
-#ifndef HAVE_REALLOCARRAY
-#undef reallocarray
-
-#include <sys/types.h>
-#include <errno.h>
-#ifdef HAVE_STDINT_H
-#include <stdint.h>
-#endif
-#include <stdlib.h>
-
-void *reallocarray(void *, size_t, size_t);
-
-/*
- * 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)
-{
-	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
-	    nmemb > 0 && SIZE_MAX / nmemb < size) {
-		errno = ENOMEM;
-		return NULL;
-	}
-	return realloc(optr, size * nmemb);
-}
-#endif /* HAVE_REALLOCARRAY */
diff --git a/src/flexint.h b/src/flexint.h
index f9fa80c..43bb3a8 100644
--- a/src/flexint.h
+++ b/src/flexint.h
@@ -58,6 +58,10 @@ typedef unsigned int flex_uint32_t;
 #define UINT32_MAX             (4294967295U)
 #endif
 
+#ifndef SIZE_MAX
+#define SIZE_MAX               (~(size_t)0)
+#endif
+
 #endif /* ! C99 */
 
 #endif /* ! FLEXINT_H */
diff --git a/src/misc.c b/src/misc.c
index 6eee161..e17b1a2 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -142,9 +142,14 @@ void add_action (const char *new_text)
 void   *allocate_array (int size, size_t element_size)
 {
 	void *mem;
-	size_t  num_bytes = element_size * (size_t) size;
-
-	mem = malloc(num_bytes);
+#if HAVE_REALLOCARRAY
+	/* reallocarray has built-in overflow detection */
+	mem = reallocarray(NULL, (size_t) size, element_size);
+#else
+	size_t num_bytes = (size_t) size * element_size;
+	mem = (size && SIZE_MAX / (size_t) size < element_size) ? NULL :
+		malloc(num_bytes);
+#endif
 	if (!mem)
 		flexfatal (_
 			   ("memory allocation failed in allocate_array()"));
@@ -681,9 +686,14 @@ char   *readable_form (int c)
 void   *reallocate_array (void *array, int size, size_t element_size)
 {
 	void *new_array;
-	size_t  num_bytes = element_size * (size_t) size;
-
-	new_array = realloc(array, num_bytes);
+#if HAVE_REALLOCARRAY
+	/* reallocarray has built-in overflow detection */
+	new_array = reallocarray(array, (size_t) size, element_size);
+#else
+	size_t num_bytes = (size_t) size * element_size;
+	new_array = (size && SIZE_MAX / (size_t) size < element_size) ? NULL :
+		realloc(array, num_bytes);
+#endif
 	if (!new_array)
 		flexfatal (_("attempt to increase array size failed"));
 
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