From 1e306fd64276aaa68eae4ffa26b68cd84092c37e Mon Sep 17 00:00:00 2001
From: sin
Date: Thu, 29 Jan 2015 10:47:54 +0000
Subject: Trap if memcpy() pointers are overlapping

Maybe this should only be done if _FORTIFY_SOURCE > 1.
---
 include/string.h | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'include')

diff --git a/include/string.h b/include/string.h
index 565f70e..60629d1 100644
--- a/include/string.h
+++ b/include/string.h
@@ -10,7 +10,13 @@ void *
 __fortify_memcpy(void *__restrict dest, const void *__restrict src, size_t n)
 {
 	size_t bos = __builtin_object_size(dest, 0);
+	char *d = dest;
+	const char *s = src;
 
+	/* trap if pointers are overlapping */
+	if ((d <= s && d + n > s) ||
+	    (s <= d && s + n > d))
+		__builtin_trap();
 	if (n > bos)
 		__builtin_trap();
 	return memcpy(dest, src, n);
-- 
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