netdev - [PATCH net-next v1 7/7] netfilter: nf_conntrack: allow early drop of offloaded UDP conns

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230110133023.2366381-8-vladbu@nvidia.com>
Date:   Tue, 10 Jan 2023 14:30:23 +0100
From:   Vlad Buslov <vladbu@...dia.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <pablo@...filter.org>
CC:     <netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
        <jhs@...atatu.com>, <xiyou.wangcong@...il.com>, <jiri@...nulli.us>,
        <ozsh@...dia.com>, <marcelo.leitner@...il.com>,
        <simon.horman@...igine.com>, Vlad Buslov <vladbu@...dia.com>
Subject: [PATCH net-next v1 7/7] netfilter: nf_conntrack: allow early drop of offloaded UDP conns

Both synchronous early drop algorithm and asynchronous gc worker completely
ignore connections with IPS_OFFLOAD_BIT status bit set. With new
functionality that enabled UDP NEW connection offload in action CT
malicious user can flood the conntrack table with offloaded UDP connections
by just sending a single packet per 5tuple because such connections can no
longer be deleted by early drop algorithm.

To mitigate the issue allow both early drop and gc to consider offloaded
UDP connections for deletion.

Signed-off-by: Vlad Buslov <vladbu@...dia.com>
---
 net/netfilter/nf_conntrack_core.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 496c4920505b..52b824a60176 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1374,9 +1374,6 @@ static unsigned int early_drop_list(struct net *net,
 	hlist_nulls_for_each_entry_rcu(h, n, head, hnnode) {
 		tmp = nf_ct_tuplehash_to_ctrack(h);
 
-		if (test_bit(IPS_OFFLOAD_BIT, &tmp->status))
-			continue;
-
 		if (nf_ct_is_expired(tmp)) {
 			nf_ct_gc_expired(tmp);
 			continue;
@@ -1446,11 +1443,14 @@ static bool gc_worker_skip_ct(const struct nf_conn *ct)
 static bool gc_worker_can_early_drop(const struct nf_conn *ct)
 {
 	const struct nf_conntrack_l4proto *l4proto;
+	u8 protonum = nf_ct_protonum(ct);
 
+	if (test_bit(IPS_OFFLOAD_BIT, &ct->status) && protonum != IPPROTO_UDP)
+		return false;
 	if (!test_bit(IPS_ASSURED_BIT, &ct->status))
 		return true;
 
-	l4proto = nf_ct_l4proto_find(nf_ct_protonum(ct));
+	l4proto = nf_ct_l4proto_find(protonum);
 	if (l4proto->can_early_drop && l4proto->can_early_drop(ct))
 		return true;
 
@@ -1507,7 +1507,8 @@ static void gc_worker(struct work_struct *work)
 
 			if (test_bit(IPS_OFFLOAD_BIT, &tmp->status)) {
 				nf_ct_offload_timeout(tmp);
-				continue;
+				if (!nf_conntrack_max95)
+					continue;
 			}
 
 			if (expired_count > GC_SCAN_EXPIRED_MAX) {
-- 
2.38.1