Re: [PATCH 07/14] net: sched: use reference counting action init

Jiri Pirko
2018-05-15T11:39:58Z

Tue, May 15, 2018 at 01:32:51PM CEST, vladbu@mellanox.com wrote:
>
>On Tue 15 May 2018 at 11:24, Jiri Pirko <jiri@resnulli.us> wrote:
>> Mon, May 14, 2018 at 04:27:08PM CEST, vladbu@mellanox.com wrote:
>>>Change action API to assume that action init function always takes
>>>reference to action, even when overwriting existing action. This is
>>>necessary because action API continues to use action pointer after init
>>>function is done. At this point action becomes accessible for concurrent
>>>modifications so user must always hold reference to it.
>>>
>>>Implement helper put list function to atomically release list of actions
>>>after action API init code is done using them.
>>>
>>>Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
>>>---
>>> net/sched/act_api.c | 38 +++++++++++++++++---------------------
>>> 1 file changed, 17 insertions(+), 21 deletions(-)
>>>
>>
>> [...]
>>
>>
>>>@@ -1196,8 +1190,7 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n,
>>> return ret;
>>> }
>>> err:
>>>- if (event != RTM_GETACTION)
>>
>> Howcome you do this for RTM_GETACTION now too? Where is the related
>> "get"?
>
>In patch 5. There is always a possibility of concurrent delete without
>rtnl lock so all usages of action pointers were converted to hold
>reference to action.

So that means that if you run kernel in between, with patch 5 but
without patch 7 and you do RTM_GETACTION, you leak a reference, right?

>
>>
>>
>>>- tcf_action_destroy(&actions, 0);
>>>+ tcf_action_put_lst(&actions);
>>> return ret;
>>> }
>>>
>>
>> [...]
>