fix for internal redirection flags colliding with open/fcntl flags; call memfd_create with MFD_NOEXEC_SEAL; fix for setting $BASH in su-started login shell; fix for unsetting $REPLY after nofork comsubs

lib/sh/anonfile.c

@@ -37,6 +37,10 @@
 
 static int anonunlink (const char *);
 
+#if defined (HAVE_MEMFD_CREATE) && !defined (MFD_NOEXEC_SEAL)
+#  define MFD_NOEXEC_SEAL 0
+#endif
+
 #if defined (HAVE_SHM_OPEN)
 #ifndef O_NOFOLLOW
 #  define O_NOFOLLOW 0
@@ -104,7 +108,7 @@ anonopen (const char *name, int flags, char **fn)
 
 #if defined (HAVE_MEMFD_CREATE)
   /* "Names do not affect the behavior of the file descriptor." */
-  fd = memfd_create ("anonopen", 0);
+  fd = memfd_create ("anonopen", MFD_NOEXEC_SEAL);
   if (fd >= 0)
     {
       if (fn)