Trap if memcpy() pointers are overlapping

Maybe this should only be done if _FORTIFY_SOURCE > 1.

1 files changed, 6 insertions, 0 deletions

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);