net: openvswitch: Fix Use-After-Free in ovs_ct_exit

Since kfree_rcu, which is called in the hlist_for_each_entry_rcu traversal
of ovs_ct_limit_exit, is not part of the RCU read critical section, it
is possible that the RCU grace period will pass during the traversal and
the key will be free.

To prevent this, it should be changed to hlist_for_each_entry_safe.

Fixes: 11efd5cb04a1 ("openvswitch: Support conntrack zone limit")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://lore.kernel.org/r/ZiYvzQN/Ry5oeFQW@v4bel-B760M-AORUS-ELITE-AX
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 74b63cdb59923a95dd03a9c2c540af702564873a..2928c142a2ddb3a0d9b1937fdb4ddd37322b3f45 100644 (file)
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -1593,9 +1593,9 @@ static void ovs_ct_limit_exit(struct net *net, struct ovs_net *ovs_net)
        for (i = 0; i < CT_LIMIT_HASH_BUCKETS; ++i) {
                struct hlist_head *head = &info->limits[i];
                struct ovs_ct_limit *ct_limit;
+               struct hlist_node *next;
 
-               hlist_for_each_entry_rcu(ct_limit, head, hlist_node,
-                                        lockdep_ovsl_is_held())
+               hlist_for_each_entry_safe(ct_limit, next, head, hlist_node)
                        kfree_rcu(ct_limit, rcu);
        }
        kfree(info->limits);