netfilter: ctnetlink: fix conntrack creation race
Conntrack creation through ctnetlink has two races:
- the timer may expire and free the conntrack concurrently, causing an
invalid memory access when attempting to put it in the hash tables
- an identical conntrack entry may be created in the packet processing
path in the time between the lookup and hash insertion
Hold the conntrack lock between the lookup and insertion to avoid this.
Reported-by: Zoltan Borbely <bozo@andrews.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 622d7c6..233fdd2 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -305,9 +305,7 @@
hash = hash_conntrack(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
repl_hash = hash_conntrack(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
- spin_lock_bh(&nf_conntrack_lock);
__nf_conntrack_hash_insert(ct, hash, repl_hash);
- spin_unlock_bh(&nf_conntrack_lock);
}
EXPORT_SYMBOL_GPL(nf_conntrack_hash_insert);
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index a040d46..3b009a3 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1090,7 +1090,7 @@
struct nf_conn_help *help;
struct nf_conntrack_helper *helper;
- ct = nf_conntrack_alloc(&init_net, otuple, rtuple, GFP_KERNEL);
+ ct = nf_conntrack_alloc(&init_net, otuple, rtuple, GFP_ATOMIC);
if (ct == NULL || IS_ERR(ct))
return -ENOMEM;
@@ -1212,13 +1212,14 @@
atomic_inc(&master_ct->ct_general.use);
}
- spin_unlock_bh(&nf_conntrack_lock);
err = -ENOENT;
if (nlh->nlmsg_flags & NLM_F_CREATE)
err = ctnetlink_create_conntrack(cda,
&otuple,
&rtuple,
master_ct);
+ spin_unlock_bh(&nf_conntrack_lock);
+
if (err < 0 && master_ct)
nf_ct_put(master_ct);