Ticket #3025: race condition when creating temporary directory.

When there's no mc-tmpdir and a user tries to start two mc sessions
simultaneously, sometimes (in one out of ten attempts on my machine) one
mc session emits the following error message:

Cannot create temporary directory /tmp/mc-lars: File exists (17)
Temporary files will be created in /tmp
Press any key to continue...

Steps to reproduce:

# rm /tmp/mc-$(whoami) -rf
# uxterm -e mc & uxterm -e mc

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

lib/vfs/interface.c

@@ -840,20 +840,20 @@ mc_tmpdir (void)
 
     canonicalize_pathname (buffer);
 
-    if (lstat (buffer, &st) == 0)
+    /* Try to create directory */
+    if (mkdir (buffer, S_IRWXU) != 0)
     {
-        /* Sanity check for existing directory */
-        if (!S_ISDIR (st.st_mode))
-            error = _("%s is not a directory\n");
-        else if (st.st_uid != getuid ())
-            error = _("Directory %s is not owned by you\n");
-        else if (((st.st_mode & 0777) != 0700) && (chmod (buffer, 0700) != 0))
-            error = _("Cannot set correct permissions for directory %s\n");
-    }
-    else
-    {
-        /* Need to create directory */
-        if (mkdir (buffer, S_IRWXU) != 0)
+        if (errno == EEXIST && lstat (buffer, &st) == 0)
+        {
+            /* Sanity check for existing directory */
+            if (!S_ISDIR (st.st_mode))
+                error = _("%s is not a directory\n");
+            else if (st.st_uid != getuid ())
+                error = _("Directory %s is not owned by you\n");
+            else if (((st.st_mode & 0777) != 0700) && (chmod (buffer, 0700) != 0))
+                error = _("Cannot set correct permissions for directory %s\n");
+        }
+        else
         {
             fprintf (stderr,
                      _("Cannot create temporary directory %s: %s\n"),