Per summary, posting a large amount of data to a service catalog item will crash, returning nothing *and* also manages to destroy the users session, requiring them to log in again.

The posted data seems to require newlines.

STEPS 

1. Generate a lot of text: 
    perl -e 'for ($i=1; $i<=10240; $i++) {print "X" x 100; print "\n"}; '|xclip
   is big enough
2. Got to a SC item with a textfield
3. Paste in data
4. See stack trace in production.log (even without submitting form)
5. See session is dead, requiring reloading the page, logging in again

Stack trace looks like
[----] W, [2017-11-14T16:22:29.701857 #1925:1e4086c]  WARN -- : Can't verify CSRF token authenticity.
[----] F, [2017-11-14T16:22:29.702114 #1925:1e4086c] FATAL -- : Error caught: [ActionController::InvalidAuthenticityToken] ActionController::InvalidAuthenticityToken
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/request_forgery_protection.rb:195:in `handle_unverified_request'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/request_forgery_protection.rb:223:in `handle_unverified_request'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/request_forgery_protection.rb:218:in `verify_authenticity_token'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:382:in `block in make_lambda'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:150:in `block (2 levels) in halting_and_conditional'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/abstract_controller/callbacks.rb:12:in `block (2 levels) in <module:Callbacks>'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:151:in `block in halting_and_conditional'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:454:in `block in call'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:454:in `each'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:454:in `call'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:101:in `__run_callbacks__'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:750:in `_run_process_action_callbacks'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/callbacks.rb:90:in `run_callbacks'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/abstract_controller/callbacks.rb:19:in `process_action'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/rescue.rb:20:in `process_action'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/instrumentation.rb:32:in `block in process_action'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/notifications.rb:164:in `block in instrument'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/opt/rh/cfme-gemset/gems/activesupport-5.0.3/lib/active_support/notifications.rb:164:in `instrument'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal/params_wrapper.rb:248:in `process_action'
/opt/rh/cfme-gemset/gems/activerecord-5.0.3/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/abstract_controller/base.rb:126:in `process'
/opt/rh/cfme-gemset/gems/actionview-5.0.3/lib/action_view/rendering.rb:30:in `process'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal.rb:190:in `dispatch'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_controller/metal.rb:262:in `dispatch'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/routing/route_set.rb:50:in `dispatch'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/routing/route_set.rb:32:in `serve'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/journey/router.rb:39:in `block in serve'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/journey/router.rb:26:in `each'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/journey/router.rb:26:in `serve'
/opt/rh/cfme-gemset/gems/actionpack-5.0.3/lib/action_dispatch/routing/route_set.rb:725:in `call'
/opt/rh/cfme-gemset/gems/secure_headers-3.0.3/lib/secure_headers/middleware.rb:10:in `call'
/opt/rh/cfme-gemset/gems/rack-2.0.3/lib/rack/etag.rb:25:in `call'

......