From: Guillaume Nault <gnault@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
---
net/core/net_namespace.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -192,9 +192,9 @@ static int net_eq_idr(int id, void *net,
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
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 n
{
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_buf
.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;
