Re: [Patch net] net_sched: reorder pernet ops and act ops registrations

From: Cong Wang <redacted>
Date: Tue, 11 Oct 2016 10:56:45 -0700

Krister reported a kernel NULL pointer dereference after
tcf_action_init_1() invokes a_o->init(), it is a race condition
where one thread calling tcf_register_action() to initialize
the netns data after putting act ops in the global list and
the other thread searching the list and then calling
a_o->init(net, ...).

Fix this by moving the pernet ops registration before making
the action ops visible. This is fine because: a) we don't
rely on act_base in pernet ops->init(), b) in the worst case we
have a fully initialized netns but ops is still not ready so
new actions still can't be created.

Reported-by: Krister Johansen <redacted>
Tested-by: Krister Johansen <redacted>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <redacted>

Applied and queued up for -stable, thanks.