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alistair23-linux
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net: sched: cls_cgroup use RCU 

Make cgroup classifier safe for RCU.

Also drops the calls in the classify routine that were doing a
rcu_read_lock()/rcu_read_unlock(). If the rcu_read_lock() isn't held
entering this routine we have issues with deleting the classifier
chain so remove the unnecessary rcu_read_lock()/rcu_read_unlock()
pair noting all paths AFAIK hold rcu_read_lock.

If there is a case where classify is called without the rcu read lock
then an rcu splat will occur and we can correct it.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
John Fastabend 2014-09-12 20:06:26 -07:00 committed by David S. Miller
parent c8b9affec5
commit c7953ef230
1 changed files with 41 additions and 26 deletions
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67
net/sched/cls_cgroup.c
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@ -22,17 +22,17 @@ struct cls_cgroup_head {
u32 handle;
struct tcf_exts exts;
struct tcf_ematch_tree ematches;
struct tcf_proto *tp;
struct rcu_head rcu;
};
static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct cls_cgroup_head *head = tp->root;
struct cls_cgroup_head *head = rcu_dereference_bh(tp->root);
u32 classid;
rcu_read_lock();
classid = task_cls_state(current)->classid;
rcu_read_unlock();
/*
* Due to the nature of the classifier it is required to ignore all
@ -80,13 +80,25 @@ static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX + 1] = {
[TCA_CGROUP_EMATCHES] = { .type = NLA_NESTED },
};
static void cls_cgroup_destroy_rcu(struct rcu_head *root)
{
struct cls_cgroup_head *head = container_of(root,
struct cls_cgroup_head,
rcu);
tcf_exts_destroy(head->tp, &head->exts);
tcf_em_tree_destroy(head->tp, &head->ematches);
kfree(head);
}
static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
struct tcf_proto *tp, unsigned long base,
u32 handle, struct nlattr **tca,
unsigned long *arg, bool ovr)
{
struct nlattr *tb[TCA_CGROUP_MAX + 1];
struct cls_cgroup_head *head = tp->root;
struct cls_cgroup_head *head = rtnl_dereference(tp->root);
struct cls_cgroup_head *new;
struct tcf_ematch_tree t;
struct tcf_exts e;
int err;
@ -94,25 +106,24 @@ static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
if (!tca[TCA_OPTIONS])
return -EINVAL;
if (head == NULL) {
if (!handle)
return -EINVAL;
if (!head && !handle)
return -EINVAL;
head = kzalloc(sizeof(*head), GFP_KERNEL);
if (head == NULL)
return -ENOBUFS;
tcf_exts_init(&head->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
head->handle = handle;
tcf_tree_lock(tp);
tp->root = head;
tcf_tree_unlock(tp);
}
if (handle != head->handle)
if (head && handle != head->handle)
return -ENOENT;
new = kzalloc(sizeof(*head), GFP_KERNEL);
if (!new)
return -ENOBUFS;
if (head) {
new->handle = head->handle;
} else {
tcf_exts_init(&new->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
new->handle = handle;
}
new->tp = tp;
err = nla_parse_nested(tb, TCA_CGROUP_MAX, tca[TCA_OPTIONS],
cgroup_policy);
if (err < 0)
@ -127,20 +138,24 @@ static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
if (err < 0)
return err;
tcf_exts_change(tp, &head->exts, &e);
tcf_em_tree_change(tp, &head->ematches, &t);
tcf_exts_change(tp, &new->exts, &e);
tcf_em_tree_change(tp, &new->ematches, &t);
rcu_assign_pointer(tp->root, new);
if (head)
call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
return 0;
}
static void cls_cgroup_destroy(struct tcf_proto *tp)
{
struct cls_cgroup_head *head = tp->root;
struct cls_cgroup_head *head = rtnl_dereference(tp->root);
if (head) {
tcf_exts_destroy(tp, &head->exts);
tcf_em_tree_destroy(tp, &head->ematches);
kfree(head);
RCU_INIT_POINTER(tp->root, NULL);
kfree_rcu(head, rcu);
}
}
@ -151,7 +166,7 @@ static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg)
static void cls_cgroup_walk(struct tcf_proto *tp, struct tcf_walker *arg)
{
struct cls_cgroup_head *head = tp->root;
struct cls_cgroup_head *head = rtnl_dereference(tp->root);
if (arg->count < arg->skip)
goto skip;
@ -167,7 +182,7 @@ skip:
static int cls_cgroup_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
struct sk_buff *skb, struct tcmsg *t)
{
struct cls_cgroup_head *head = tp->root;
struct cls_cgroup_head *head = rtnl_dereference(tp->root);
unsigned char *b = skb_tail_pointer(skb);
struct nlattr *nest;