** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
       Status: New => Triaged

** Tags added: kernel-da-key

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  Kernel CIFS Module ignores USER_SESSION_DELETED PDUs and holds onto
  dead sessions.

Status in Linux:
Status in linux package in Ubuntu:

Bug description:
  The cifs kernel module currently ignores the nt_status USER_SESSION_DELETED 
PDUs sent to it from remote SMB2+ peers and holds onto clearly dead SMB2+ 
sessions as a result.

  This is causing issues, as it appears that the kernel only reconnects
  after a delay period, during which time all IO to that network share
  (with that session id) results in an I/O error for the user; all the
  while the kernel is repeatedly resubmitting the requests in the
  background with the server just responding to each of them with yet
  more USER_SESSION_DELETED packets.

  This is contrasting to the behaviour on Windows clients - whereby if
  the response the client gets is USER_SESSION_DELETED, it drops that
  session and reconnects - transparently to the user.

  This causes massive issues multiuser mounts (as is the case for me),
  as if a users SMB session is deleted by the server for any reason,
  that user essentially loses all access to that share for extended
  periods, until the cifs module sees fit to treat that session as dead
  and renegotiate or an admin intervenes.

  # Reproducing
  Reproducing the issue is easily done, establish an SMB2+ mount to a Windows 
Server machine, open any directory on client to establish a session, then 
simply terminate that SMB session from the servers MMC console, if you then try 
and run any queries against that mountpoint on the client you will just end up 
with a string of I/O errors because its trying to use a session id which is 

  For reference I'm testing using the following mount options:

  # Affects
  This affects all kernel releases that I've tested(including the kernel 
mainline), and hence I've reported it upstream, however I'm recording it here 
as well for reference purposes.

  ## Additional Reference Info

  Current Version Sig: Ubuntu 4.4.0-78.99-generic 4.4.62

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