BugLink: https://bugs.launchpad.net/bugs/1883916

commit af87ae46 upstream.

There's no point in checking for duplicate sessions at the beginning of
l2tp_nl_cmd_session_create(); the ->session_create() callbacks already
return -EEXIST when the session already exists.

Furthermore, even if l2tp_session_find() returns NULL, a new session
might be created right after the test. So relying on ->session_create()
to avoid duplicate session is the only sane behaviour.
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>