Abuse __cxa_thread_atexit_impl to free TLS pointers.

Author: besser82

crypt-gensalt-static.c

@@ -36,6 +36,9 @@ crypt_gensalt (const char *prefix, unsigned long count,
       obuf = malloc (CRYPT_GENSALT_OUTPUT_SIZE);
       if (!obuf)
         return 0;
+#if HAVE_GLIBC_CXA_THREAD_ATEXIT_IMPL
+      __cxa_thread_atexit_impl (free, obuf, obuf);
+#endif
     }
 
   return crypt_gensalt_rn (prefix, count, rbytes, nrbytes,

crypt-port.h

@@ -122,6 +122,19 @@ typedef union
 /* ARRAY_SIZE is used in tests.  */
 #define ARRAY_SIZE(a_)  (sizeof (a_) / sizeof ((a_)[0]))
 
+/* Thread local storage needs a way to be destructed, when the thread
+   is terminated.  Using a weak defined function from glibc >= 2.18
+   is the only way we currently know about.  */
+#if defined __GLIBC__ && ((__GLIBC__ == 2 && \
+    defined __GLIBC_MINOR__ && __GLIBC_MINOR__ >= 18) || \
+    __GLIBC__ >= 3)
+#define HAVE_GLIBC_CXA_THREAD_ATEXIT_IMPL 1
+extern int __cxa_thread_atexit_impl (void (*func) (void *), void *arg,
+                                     void *d);
+#else
+#define HAVE_GLIBC_CXA_THREAD_ATEXIT_IMPL 0
+#endif
+
 /* Provide a guaranteed way to erase sensitive memory at the best we
    can, given the possibilities of the system.  */
 #if defined HAVE_MEMSET_S

crypt-static.c

@@ -51,6 +51,9 @@ crypt (const char *key, const char *setting)
           return 0;
 #endif
         }
+#if HAVE_GLIBC_CXA_THREAD_ATEXIT_IMPL
+      __cxa_thread_atexit_impl (free, nr_crypt_ctx, nr_crypt_ctx);
+#endif
     }
 
   return crypt_r (key, setting, nr_crypt_ctx);