[PATCH net-next 07/14] net: sched: act_sample: remove dependency on rtnl lock

[Vlad Buslov]

Use tcf spinlock to protect private sample action data from concurrent
modification during dump and init.

Signed-off-by: Vlad Buslov <vla...@mellanox.com>
---
 net/sched/act_sample.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c
index 2608ccc83e5e..81071afe1b43 100644
--- a/net/sched/act_sample.c
+++ b/net/sched/act_sample.c
@@ -80,11 +80,13 @@ static int tcf_sample_init(struct net *net, struct nlattr 
*nla,
        }
        s = to_sample(*a);
 
+       spin_lock(&s->tcf_lock);
        s->tcf_action = parm->action;
        s->rate = nla_get_u32(tb[TCA_SAMPLE_RATE]);
        s->psample_group_num = nla_get_u32(tb[TCA_SAMPLE_PSAMPLE_GROUP]);
        psample_group = psample_group_get(net, s->psample_group_num);
        if (!psample_group) {
+               spin_unlock(&s->tcf_lock);
                tcf_idr_release(*a, bind);
                return -ENOMEM;
        }
@@ -94,6 +96,7 @@ static int tcf_sample_init(struct net *net, struct nlattr 
*nla,
                s->truncate = true;
                s->trunc_size = nla_get_u32(tb[TCA_SAMPLE_TRUNC_SIZE]);
        }
+       spin_unlock(&s->tcf_lock);
 
        if (ret == ACT_P_CREATED)
                tcf_idr_insert(tn, *a);
@@ -105,7 +108,8 @@ static void tcf_sample_cleanup(struct tc_action *a)
        struct tcf_sample *s = to_sample(a);
        struct psample_group *psample_group;
 
-       psample_group = rtnl_dereference(s->psample_group);
+       /* last reference to action, no need to lock */
+       psample_group = rcu_dereference_protected(s->psample_group, 1);
        RCU_INIT_POINTER(s->psample_group, NULL);
        if (psample_group)
                psample_group_put(psample_group);
@@ -174,12 +178,13 @@ static int tcf_sample_dump(struct sk_buff *skb, struct 
tc_action *a,
        struct tcf_sample *s = to_sample(a);
        struct tc_sample opt = {
                .index      = s->tcf_index,
-               .action     = s->tcf_action,
                .refcnt     = refcount_read(&s->tcf_refcnt) - ref,
                .bindcnt    = atomic_read(&s->tcf_bindcnt) - bind,
        };
        struct tcf_t t;
 
+       spin_lock(&s->tcf_lock);
+       opt.action = s->tcf_action;
        if (nla_put(skb, TCA_SAMPLE_PARMS, sizeof(opt), &opt))
                goto nla_put_failure;
 
@@ -196,9 +201,12 @@ static int tcf_sample_dump(struct sk_buff *skb, struct 
tc_action *a,
 
        if (nla_put_u32(skb, TCA_SAMPLE_PSAMPLE_GROUP, s->psample_group_num))
                goto nla_put_failure;
+       spin_unlock(&s->tcf_lock);
+
        return skb->len;
 
 nla_put_failure:
+       spin_unlock(&s->tcf_lock);
        nlmsg_trim(skb, b);
        return -1;
 }
-- 
2.7.5