tmpdir filling up with attachments

[adamjt]

We're building out our Communication object attachments with this, where @msg is a Postmark::Mitt object:

if !@msg.attachments.empty?
@msg.attachments.each do |att|
comm.attachments.build(:file => att.read)
end
end

comm.save!

In the save hook for that model the attachments are sent to S3 via paperclip, but /tmp/ is filling up with the processed files. Is there a different way we should be doing it to ensure that cruft gets cleaned up?