Only crash on overflow for realpath()

1 files changed, 11 insertions, 3 deletions

diff --git a/include/stdlib.h b/include/stdlib.h
index f89341f..26c7e44 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -35,15 +35,23 @@ extern "C" {
 #undef realpath
 _FORTIFY_FN(realpath) char *realpath(const char *__p, char *__r)
 {
-        size_t __b;
+        size_t __b = __builtin_object_size(__r, 0);
 
         if (__r) {
 #ifndef PATH_MAX
 #error PATH_MAX unset. A fortified realpath will not work.
 #else
-                __b = __builtin_object_size(__r, 0);
-                if (PATH_MAX > __b)
+                char __buf[PATH_MAX], *__ret;
+                size_t __l;
+
+                __ret = __orig_realpath(__p, __buf);
+                if (!__ret)
+                        return NULL;
+                __l = __builtin_strlen(__ret) + 1;
+                if (__l > __b)
                         __builtin_trap();
+                __builtin_memcpy(__r, __ret, __l);
+                return __r;
 #endif
         }
         return __orig_realpath(__p, __r);