** Changed in: linux (Ubuntu)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu)
Status: New => Triaged
** Tags added: kernel-da-key
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https://bugs.launchpad.net/bugs/1707167
Title:
Kernel CIFS Module ignores USER_SESSION_DELETED PDUs and holds onto
dead sessions.
Status in Linux:
Unknown
Status in linux package in Ubuntu:
Triaged
Bug description:
#Summary
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
dead.
For reference I'm testing using the following mount options:
vers=3.02,multiuser,sec=ntlmsspi,file_mode=0750,dir_mode=0755,cache=none,credentials=/etc/smb.credentials.conf
# 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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