Commit c7953ef2 authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
Browse files

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: default avatarJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c8b9affe

net/sched/cls_cgroup.c

+39 −24
Original line number Diff line number Diff line
@@ -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)

	if (!head && !handle)

		return -EINVAL;



		head = kzalloc(sizeof(*head), GFP_KERNEL);

		if (head == NULL)

			return -ENOBUFS;

	if (head && handle != head->handle)

		return -ENOENT;



		tcf_exts_init(&head->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);

		head->handle = handle;

	new = kzalloc(sizeof(*head), GFP_KERNEL);

	if (!new)

		return -ENOBUFS;



		tcf_tree_lock(tp);

		tp->root = head;

		tcf_tree_unlock(tp);

	if (head) {

		new->handle = head->handle;

	} else {

		tcf_exts_init(&new->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);

		new->handle = handle;

	}



	if (handle != head->handle)

		return -ENOENT;



	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;

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