[BUG, linux-next] spawn PID 1 without CLONE_FS, wireless inop

[Jeremiah Mahler]

all,

The wireless network interface has become inoperative when running
linux-next 20141216 on a Lenovo Carbon X1.  It is completely
non-existent and `ip addr` doesn't show it.  A bisect has found that
the bug was introduced by the following commit.

  commit 9d328afb18f05c25686102ad890a67bb3ca38aab
  Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
  Date:   Thu Dec 11 22:34:21 2014 -0500
  
      spawn PID 1 without CLONE_FS, give kernel threads zero umask
      
      Don't give PID 1 init_fs, give it a copy of its own when it's
  spawned.
      Then we can make init_fs.umode zero, and have both the PID 1 and
      everything that gets spawned by call_usermodehelper() set
  ->fs->umask
      to old value (0022) early on.
      
      Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

Below is my network interface information.  And the iwlwifi modules are
being used.

  $ lspci
  ...
  03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205
  [Taylor Peak] (rev 96)
  ...

And the patch which introduced this bug is included below.