Messages in this thread | | | Date | Fri, 28 Jul 2017 17:11:38 +0200 | From | Daniel Borkmann <> | Subject | Re: [PATCH net-next 3/3] tap: XDP support |
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On 07/28/2017 05:46 AM, Michael S. Tsirkin wrote: > 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().
+1, good catch Jakub.
> I suspect you need to sync RCU or something before that.
No, see for example generic_xdp_install().
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