Please apply the following patch to linux-stable 4.4.y: commit 205e1e255c479f3fd77446415706463b282f94e4 ppp: defer netns reference release for ppp channel
This is already present in 4.8.y and fixes an issue with ppp channels that would otherwise cause a BUG() in ppp_pernet while a global ppp mutex is held, preventing further ppp connections from being established. The issue is reproducible by having pppd use a PPPoE server that closes new connections immediately (e.g. rp-pppoe "pppoe-server -q /bin/true"). -- Simon Arlott
