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netns: protect netns ID lookups with RCU

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commit 2dce224f469f060b9998a5a869151ef83c08ce77 upstream.

__peernet2id() can be protected by RCU as it only calls idr_for_each(),
which is RCU-safe, and never modifies the nsid table.

rtnl_net_dumpid() can also do lockless lookups. It does two nested
idr_for_each() calls on nsid tables (one direct call and one indirect
call because of rtnl_net_dumpid_one() calling __peernet2id()). The
netnsid tables are never updated. Therefore it is safe to not take the
nsid_lock and run within an RCU-critical section instead.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
This commit is contained in:
Guillaume Nault 2020-01-13 22:39:22 +01:00 committed by Greg Kroah-Hartman
parent 1d3e3d5697
commit f94601e19d
1 changed files with 10 additions and 8 deletions
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18
net/core/net_namespace.c
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@ -192,9 +192,9 @@ static int net_eq_idr(int id, void *net, void *peer)
return 0;
}
/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc
* is set to true, thus the caller knows that the new id must be notified via
* rtnl.
/* Must be called from RCU-critical section or with nsid_lock held. If
* a new id is assigned, the bool alloc is set to true, thus the
* caller knows that the new id must be notified via rtnl.
*/
static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
{
@ -218,7 +218,7 @@ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
return NETNSA_NSID_NOT_ASSIGNED;
}
/* should be called with nsid_lock held */
/* Must be called from RCU-critical section or with nsid_lock held */
static int __peernet2id(struct net *net, struct net *peer)
{
bool no = false;
@ -261,9 +261,10 @@ int peernet2id(struct net *net, struct net *peer)
{
int id;
spin_lock_bh(&net->nsid_lock);
rcu_read_lock();
id = __peernet2id(net, peer);
spin_unlock_bh(&net->nsid_lock);
rcu_read_unlock();
return id;
}
EXPORT_SYMBOL(peernet2id);
@ -837,6 +838,7 @@ struct rtnl_net_dump_cb {
int s_idx;
};
/* Runs in RCU-critical section. */
static int rtnl_net_dumpid_one(int id, void *peer, void *data)
{
struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
@ -867,9 +869,9 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb)
.s_idx = cb->args[0],
};
spin_lock_bh(&net->nsid_lock);
rcu_read_lock();
idr_for_each(&net->netns_ids, rtnl_net_dumpid_one, &net_cb);
spin_unlock_bh(&net->nsid_lock);
rcu_read_unlock();
cb->args[0] = net_cb.idx;
return skb->len;