From 1ace027335c9ca0ae400958aded936d04505ec86 Mon Sep 17 00:00:00 2001
From: jvoisin
Date: Tue, 30 May 2023 20:46:14 +0200
Subject: Add a check for overlapping copies in strcpy

---
 include/string.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

(limited to 'include/string.h')

diff --git a/include/string.h b/include/string.h
index f08eb4c..8685bb7 100644
--- a/include/string.h
+++ b/include/string.h
@@ -107,8 +107,15 @@ _FORTIFY_FN(strcat) char *strcat(char *__d, const char *__s)
 
 _FORTIFY_FN(strcpy) char *strcpy(char *__d, const char *__s)
 {
-	size_t __b = __bos(__d, 0);
+	size_t __n = strlen(__s) + 1;
+
+	/* trap if pointers are overlapping but not if dst == src.
+	 * gcc seems to like to generate code that relies on dst == src */
+	if ((__d < __s && __d + __n > __s) ||
+	    (__s < __d && __s + __n > __d))
+		__builtin_trap();
 
+	size_t __b = __bos(__d, 0);
 	if (strlen(__s) + 1 > __b)
 		__builtin_trap();
 	return __orig_strcpy(__d, __s);
-- 
cgit v1.3