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    Subject[PATCH 4.9 15/51] net sched actions: fix refcnt when GETing of action after bind
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jamal Hadi Salim <jhs@mojatatu.com>


    [ Upstream commit 0faa9cb5b3836a979864a6357e01d2046884ad52 ]

    Demonstrating the issue:

    .. add a drop action
    $sudo $TC actions add action drop index 10

    .. retrieve it
    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 2 bind 0 installed 29 sec used 29 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    ... bug 1 above: reference is two.
    Reference is actually 1 but we forget to subtract 1.

    ... do a GET again and we see the same issue
    try a few times and nothing changes
    ~$ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 2 bind 0 installed 31 sec used 31 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    ... lets try to bind the action to a filter..
    $ sudo $TC qdisc add dev lo ingress
    $ sudo $TC filter add dev lo parent ffff: protocol ip prio 1 \
    u32 match ip dst 127.0.0.1/32 flowid 1:1 action gact index 10

    ... and now a few GETs:
    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 3 bind 1 installed 204 sec used 204 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 4 bind 1 installed 206 sec used 206 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 5 bind 1 installed 235 sec used 235 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    .... as can be observed the reference count keeps going up.

    After the fix

    $ sudo $TC actions add action drop index 10
    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 1 bind 0 installed 4 sec used 4 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 1 bind 0 installed 6 sec used 6 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    $ sudo $TC qdisc add dev lo ingress
    $ sudo $TC filter add dev lo parent ffff: protocol ip prio 1 \
    u32 match ip dst 127.0.0.1/32 flowid 1:1 action gact index 10

    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 2 bind 1 installed 32 sec used 32 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    $ sudo $TC -s actions get action gact index 10

    action order 1: gact action drop
    random type none pass val 0
    index 10 ref 2 bind 1 installed 33 sec used 33 sec
    Action statistics:
    Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
    backlog 0b 0p requeues 0

    Fixes: aecc5cefc389 ("net sched actions: fix GETing actions")
    Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sched/act_api.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    --- a/net/sched/act_api.c
    +++ b/net/sched/act_api.c
    @@ -903,8 +903,6 @@ tca_action_gd(struct net *net, struct nl
    goto err;
    }
    act->order = i;
    - if (event == RTM_GETACTION)
    - act->tcfa_refcnt++;
    list_add_tail(&act->list, &actions);
    }

    @@ -917,7 +915,8 @@ tca_action_gd(struct net *net, struct nl
    return ret;
    }
    err:
    - tcf_action_destroy(&actions, 0);
    + if (event != RTM_GETACTION)
    + tcf_action_destroy(&actions, 0);
    return ret;
    }


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