On Fri, Jul 28, 2017 at 11:28:54AM +0800, Jason Wang wrote: > > > + old_prog = rtnl_dereference(tun->xdp_prog); > > > + if (old_prog) > > > + bpf_prog_put(old_prog); > > > + rcu_assign_pointer(tun->xdp_prog, prog); > > Is this OK? Could this lead to the program getting freed and then > > datapath accessing a stale pointer? I mean in the scenario where the > > process gets pre-empted between the bpf_prog_put() and > > rcu_assign_pointer()? > > Will call bpf_prog_put() after rcu_assign_pointer().
I suspect you need to sync RCU or something before that.
