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net: sched: act_csum: remove dependency on rtnl lock
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Use tcf lock to protect csum action struct private data from concurrent
modification in init and dump. Use rcu swap operation to reassign params
pointer under protection of tcf lock. (old params value is not used by
init, so there is no need of standalone rcu dereference step)

Remove rtnl assertion that is no longer necessary.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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w1ldptr authored and davem330 committed Aug 11, 2018
1 parent 2142236 commit b6a2b97
Showing 1 changed file with 15 additions and 9 deletions.
24 changes: 15 additions & 9 deletions net/sched/act_csum.c
Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
struct netlink_ext_ack *extack)
{
struct tc_action_net *tn = net_generic(net, csum_net_id);
struct tcf_csum_params *params_old, *params_new;
struct tcf_csum_params *params_new;
struct nlattr *tb[TCA_CSUM_MAX + 1];
struct tc_csum *parm;
struct tcf_csum *p;
Expand Down Expand Up @@ -88,20 +88,22 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
}

p = to_tcf_csum(*a);
ASSERT_RTNL();

params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
if (unlikely(!params_new)) {
tcf_idr_release(*a, bind);
return -ENOMEM;
}
params_old = rtnl_dereference(p->params);
params_new->update_flags = parm->update_flags;

spin_lock(&p->tcf_lock);
p->tcf_action = parm->action;
params_new->update_flags = parm->update_flags;
rcu_assign_pointer(p->params, params_new);
if (params_old)
kfree_rcu(params_old, rcu);
rcu_swap_protected(p->params, params_new,
lockdep_is_held(&p->tcf_lock));
spin_unlock(&p->tcf_lock);

if (params_new)
kfree_rcu(params_new, rcu);

if (ret == ACT_P_CREATED)
tcf_idr_insert(tn, *a);
Expand Down Expand Up @@ -599,11 +601,13 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
.index = p->tcf_index,
.refcnt = refcount_read(&p->tcf_refcnt) - ref,
.bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
.action = p->tcf_action,
};
struct tcf_t t;

params = rtnl_dereference(p->params);
spin_lock(&p->tcf_lock);
params = rcu_dereference_protected(p->params,
lockdep_is_held(&p->tcf_lock));
opt.action = p->tcf_action;
opt.update_flags = params->update_flags;

if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
Expand All @@ -612,10 +616,12 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
tcf_tm_dump(&t, &p->tcf_tm);
if (nla_put_64bit(skb, TCA_CSUM_TM, sizeof(t), &t, TCA_CSUM_PAD))
goto nla_put_failure;
spin_unlock(&p->tcf_lock);

return skb->len;

nla_put_failure:
spin_unlock(&p->tcf_lock);
nlmsg_trim(skb, b);
return -1;
}
Expand Down

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