Baruch Even wrote:
> Patrick McHardy wrote:
>
>>New version of the netlink_has_listeners() patch.
>>
>>Changes:
>>
>>- Fix missing listeners bitmap update when there was no delta in the
>> number of subscribed groups
>>- Use RCU to protect nltable listeners bitmap
>>
>>
>>
>>------------------------------------------------------------------------
>>
>>[NETLINK]: Add netlink_has_listeners() for checking for multicast listeners
>>
>>netlink_has_listeners() should be used to avoid unneccessary event message
>>generation if there are no listeners.
>>
>
> ...
>
>> if (nlk->flags & NETLINK_KERNEL_SOCKET) {
>>- netlink_table_grab();
>>+ unsigned long *listeners;
>>+
>>+ listeners = nl_table[sk->sk_protocol].listeners;
>>+ nl_table[sk->sk_protocol].listeners = NULL;
>>+ synchronize_rcu();
>>+ kfree(nl_table[sk->sk_protocol].listeners);
>
>
> Doesn't the NULL assignment needs to use rcu_assign_pointer()?
Thinking about it .. using RCU seems entirely unneccessary, assuming
callers don't close the kernel socket and call netlink_has_listeners()
afterwards, the pointer is always valid.
> And isn't the kfree should be on the local listeners variable as opposed
> to the "just" NULLed variable?
Thanks for catching this. I'm not sure how this slipped in, reverting
the patch using cg-admin-uncommit without editing it before shows the
correct line, kfree(listeners).
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