CVE-2016-8605: Thread-unsafe umask modification
https://bugs.alpinelinux.org/issues/6367
http://git.savannah.gnu.org/cgit/guile.git/commit/?h=stable-2.0&id=245608911698adb3472803856019bdd5670b6614

Remove 'umask' calls from 'mkdir'.
Fixes <http://bugs.gnu.org/24659>.

* libguile/filesys.c (SCM_DEFINE): Remove calls to 'umask' when MODE is
unbound; instead, use 0777 as the mode.  Update docstring to clarify
this.
* doc/ref/posix.texi (File System): Adjust accordingly.

diff -ru guile-1.8.8.orig/libguile/filesys.c guile-1.8.8/libguile/filesys.c
--- guile-1.8.8.orig/libguile/filesys.c
+++ guile-1.8.8/libguile/filesys.c
@@ -790,27 +790,22 @@
 #ifdef HAVE_MKDIR
 SCM_DEFINE (scm_mkdir, "mkdir", 1, 1, 0,
             (SCM path, SCM mode),
-	    "Create a new directory named by @var{path}.  If @var{mode} is omitted\n"
-	    "then the permissions of the directory file are set using the current\n"
-	    "umask.  Otherwise they are set to the decimal value specified with\n"
-	    "@var{mode}.  The return value is unspecified.")
+      "Create a new directory named by @var{path}.  If @var{mode} is omitted\n"
+      "then the permissions of the directory are set to @code{#o777}\n"
+      "masked with the current umask (@pxref{Processes, @code{umask}}).\n"
+      "Otherwise they are set to the value specified with @var{mode}.\n"
+      "The return value is unspecified.")
 #define FUNC_NAME s_scm_mkdir
 {
   int rv;
-  mode_t mask;
+  mode_t c_mode;
 
-  if (SCM_UNBNDP (mode))
-    {
-      mask = umask (0);
-      umask (mask);
-      STRING_SYSCALL (path, c_path, rv = mkdir (c_path, 0777 ^ mask));
-    }
-  else
-    {
-      STRING_SYSCALL (path, c_path, rv = mkdir (c_path, scm_to_uint (mode)));
-    }
+  c_mode = SCM_UNBNDP (mode) ? 0777 : scm_to_uint (mode);
+
+  STRING_SYSCALL (path, c_path, rv = mkdir (c_path, c_mode));
   if (rv != 0)
     SCM_SYSERROR;
+
   return SCM_UNSPECIFIED;
 }
 #undef FUNC_NAME