Commit 00ca9c5b authored Jan 21, 2014 by Christoph Paasch Committed by David S. Miller Jan 22, 2014

tcp: metrics: Fix rcu-race when deleting multiple entries



In bbf852b9 I introduced the tmlist, which allows to delete
multiple entries from the cache that match a specified destination if no
source-IP is specified.

However, as the cache is an RCU-list, we should not create this tmlist, as
it will change the tcpm_next pointer of the element that will be deleted
and so a thread iterating over the cache's entries while holding the
RCU-lock might get "redirected" to this tmlist.

This patch fixes this, by reverting back to the old behavior prior to
bbf852b9, which means that we simply change the tcpm_next
pointer of the previous element (pp) to jump over the one we are
deleting.
The difference is that we call kfree_rcu() directly on the cache entry,
which allows us to delete multiple entries from the list.

Fixes: bbf852b9 (tcp: metrics: Delete all entries matching a certain destination)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7705b104

net/ipv4/tcp_metrics.c

+5 −9

Original line number	Diff line number	Diff line
		@@ -1019,13 +1019,13 @@ static int tcp_metrics_flush_all(struct net *net)
		static int tcp_metrics_nl_cmd_del(struct sk_buff skb, struct genl_info info)
		{
		struct tcpm_hash_bucket *hb;
		struct tcp_metrics_block tm, tmlist = NULL;
		struct tcp_metrics_block *tm;
		struct tcp_metrics_block __rcu **pp;
		struct inetpeer_addr saddr, daddr;
		unsigned int hash;
		struct net *net = genl_info_net(info);
		int ret;
		bool src = true;
		bool src = true, found = false;

		ret = parse_nl_addr(info, &daddr, &hash, 1);
		if (ret < 0)
		@@ -1044,19 +1044,15 @@ static int tcp_metrics_nl_cmd_del(struct sk_buff skb, struct genl_info info)
		if (addr_same(&tm->tcpm_daddr, &daddr) &&
		(!src \|\| addr_same(&tm->tcpm_saddr, &saddr))) {
		*pp = tm->tcpm_next;
		tm->tcpm_next = tmlist;
		tmlist = tm;
		kfree_rcu(tm, rcu_head);
		found = true;
		} else {
		pp = &tm->tcpm_next;
		}
		}
		spin_unlock_bh(&tcp_metrics_lock);
		if (!tmlist)
		if (!found)
		return -ESRCH;
		for (tm = tmlist; tm; tm = tmlist) {
		tmlist = tm->tcpm_next;
		kfree_rcu(tm, rcu_head);
		}
		return 0;
		}

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