Re: netlink: GPF in sock_sndtimeo

On 2016-12-09 20:13, Cong Wang wrote: > Netlink notifier can safely be converted to blocking one, I will send > a patch. I had a quick look at how that might happen. The netlink notifier chain is atomic. Would the registered callback funciton need to spawn a one-time thread to avoid blocking?

I had a look at your patch. It looks attractively simple. The audit next tree has patches queued that add an audit_reset function that will require more work. I still see some potential gaps. - If the process messes up (or the sock lookup messes up) it is reset in the kauditd thread under the audit_cmd_mutex. - If the process exits normally or is replaced due to an audit_replace error, it is reset from audit_receive_skb under the audit_cmd_mutex. - If the process dies before the kauditd thread notices, either reap it via notifier callback or it needs a check on net exit to reset. This last one appears necessary to decrement the sock refcount so the sock can be released in netlink_kernel_release(). If we want to be proactive and use the netlink notifier, we assume the overhead of adding to the netlink notifier chain and eliminate all the other reset calls under the kauditd thread. If we are ok being reactionary, then we'll at least need the net exit check on audit_sock.