[PATCH 6.18 103/198] netfilter: nfnetlink_queue: make hash table per queue

Greg Kroah-Hartman
2026-04-20T16:01:43Z

From: Florian Westphal <fw@strlen.de>

[ Upstream commit 936206e3f6ff411581e615e930263d6f8b78df9d ]

Sharing a global hash table among all queues is tempting, but
it can cause crash:

BUG: KASAN: slab-use-after-free in nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue]
[..]
nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue]
nfnetlink_rcv_msg+0x46a/0x930
kmem_cache_alloc_node_noprof+0x11e/0x450

struct nf_queue_entry is freed via kfree, but parallel cpu can still
encounter such an nf_queue_entry when walking the list.

Alternative fix is to free the nf_queue_entry via kfree_rcu() instead,
but as we have to alloc/free for each skb this will cause more mem
pressure.

Cc: Scott Mitchell <scott.k.mitch1@gmail.com>
Fixes: e19079adcd26 ("netfilter: nfnetlink_queue: optimize verdict lookup with hash table")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/netfilter/nf_queue.h | 1 -
net/netfilter/nfnetlink_queue.c | 139 +++++++++++--------------------
2 files changed, 49 insertions(+), 91 deletions(-)

diff --git a/include/net/netfilter/nf_queue.h b/include/net/netfilter/nf_queue.h
index 45eb26b2e95b3..d17035d14d96c 100644
--- a/include/net/netfilter/nf_queue.h
+++ b/include/net/netfilter/nf_queue.h
@@ -23,7 +23,6 @@ struct nf_queue_entry {
struct nf_hook_state state;
bool nf_ct_is_unconfirmed;
u16 size; /* sizeof(entry) + saved route keys */
- u16 queue_num;

/* extra space to store route keys */
};
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index a39d3b989063c..fe5942535245d 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -49,8 +49,8 @@
#endif

#define NFQNL_QMAX_DEFAULT 1024
-#define NFQNL_HASH_MIN 1024
-#define NFQNL_HASH_MAX 1048576
+#define NFQNL_HASH_MIN 8
+#define NFQNL_HASH_MAX 32768

/* We're using struct nlattr which has 16bit nla_len. Note that nla_len
* includes the header length. Thus, the maximum packet length that we
@@ -60,29 +60,10 @@
*/
#define NFQNL_MAX_COPY_RANGE (0xffff - NLA_HDRLEN)

-/* Composite key for packet lookup: (net, queue_num, packet_id) */
-struct nfqnl_packet_key {
- possible_net_t net;
- u32 packet_id;
- u16 queue_num;
-} __aligned(sizeof(u32)); /* jhash2 requires 32-bit alignment */
-
-/* Global rhashtable - one for entire system, all netns */
-static struct rhashtable nfqnl_packet_map __read_mostly;
-
-/* Helper to initialize composite key */
-static inline void nfqnl_init_key(struct nfqnl_packet_key *key,
- struct net *net, u32 packet_id, u16 queue_num)
-{
- memset(key, 0, sizeof(*key));
- write_pnet(&key->net, net);
- key->packet_id = packet_id;
- key->queue_num = queue_num;
-}
-
struct nfqnl_instance {
struct hlist_node hlist; /* global list of queues */
- struct rcu_head rcu;
+ struct rhashtable nfqnl_packet_map;
+ struct rcu_work rwork;

u32 peer_portid;
unsigned int queue_maxlen;
@@ -106,6 +87,7 @@ struct nfqnl_instance {

typedef int (*nfqnl_cmpfn)(struct nf_queue_entry *, unsigned long);

+static struct workqueue_struct *nfq_cleanup_wq __read_mostly;
static unsigned int nfnl_queue_net_id __read_mostly;

#define INSTANCE_BUCKETS 16
@@ -124,34 +106,10 @@ static inline u_int8_t instance_hashfn(u_int16_t queue_num)
return ((queue_num >> 8) ^ queue_num) % INSTANCE_BUCKETS;
}

-/* Extract composite key from nf_queue_entry for hashing */
-static u32 nfqnl_packet_obj_hashfn(const void *data, u32 len, u32 seed)
-{
- const struct nf_queue_entry *entry = data;
- struct nfqnl_packet_key key;
-
- nfqnl_init_key(&key, entry->state.net, entry->id, entry->queue_num);
-
- return jhash2((u32 *)&key, sizeof(key) / sizeof(u32), seed);
-}
-
-/* Compare stack-allocated key against entry */
-static int nfqnl_packet_obj_cmpfn(struct rhashtable_compare_arg *arg,
- const void *obj)
-{
- const struct nfqnl_packet_key *key = arg->key;
- const struct nf_queue_entry *entry = obj;
-
- return !net_eq(entry->state.net, read_pnet(&key->net)) ||
- entry->queue_num != key->queue_num ||
- entry->id != key->packet_id;
-}
-
static const struct rhashtable_params nfqnl_rhashtable_params = {
.head_offset = offsetof(struct nf_queue_entry, hash_node),
- .key_len = sizeof(struct nfqnl_packet_key),
- .obj_hashfn = nfqnl_packet_obj_hashfn,
- .obj_cmpfn = nfqnl_packet_obj_cmpfn,
+ .key_offset = offsetof(struct nf_queue_entry, id),
+ .key_len = sizeof(u32),
.automatic_shrinking = true,
.min_size = NFQNL_HASH_MIN,
.max_size = NFQNL_HASH_MAX,
@@ -190,6 +148,10 @@ instance_create(struct nfnl_queue_net *q, u_int16_t queue_num, u32 portid)
spin_lock_init(&inst->lock);
INIT_LIST_HEAD(&inst->queue_list);

+ err = rhashtable_init(&inst->nfqnl_packet_map, &nfqnl_rhashtable_params);
+ if (err < 0)
+ goto out_free;
+
spin_lock(&q->instances_lock);
if (instance_lookup(q, queue_num)) {
err = -EEXIST;
@@ -210,6 +172,8 @@ instance_create(struct nfnl_queue_net *q, u_int16_t queue_num, u32 portid)

out_unlock:
spin_unlock(&q->instances_lock);
+ rhashtable_destroy(&inst->nfqnl_packet_map);
+out_free:
kfree(inst);
return ERR_PTR(err);
}
@@ -217,15 +181,18 @@ instance_create(struct nfnl_queue_net *q, u_int16_t queue_num, u32 portid)
static void nfqnl_flush(struct nfqnl_instance *queue, nfqnl_cmpfn cmpfn,
unsigned long data);

-static void
-instance_destroy_rcu(struct rcu_head *head)
+static void instance_destroy_work(struct work_struct *work)
{
- struct nfqnl_instance *inst = container_of(head, struct nfqnl_instance,
- rcu);
+ struct nfqnl_instance *inst;

+ inst = container_of(to_rcu_work(work), struct nfqnl_instance,
+ rwork);
rcu_read_lock();
nfqnl_flush(inst, NULL, 0);
rcu_read_unlock();
+
+ rhashtable_destroy(&inst->nfqnl_packet_map);
+
kfree(inst);
module_put(THIS_MODULE);
}
@@ -234,7 +201,9 @@ static void
__instance_destroy(struct nfqnl_instance *inst)
{
hlist_del_rcu(&inst->hlist);
- call_rcu(&inst->rcu, instance_destroy_rcu);
+
+ INIT_RCU_WORK(&inst->rwork, instance_destroy_work);
+ queue_rcu_work(nfq_cleanup_wq, &inst->rwork);
}

static void
@@ -250,9 +219,7 @@ __enqueue_entry(struct nfqnl_instance *queue, struct nf_queue_entry *entry)
{
int err;

- entry->queue_num = queue->queue_num;
-
- err = rhashtable_insert_fast(&nfqnl_packet_map, &entry->hash_node,
+ err = rhashtable_insert_fast(&queue->nfqnl_packet_map, &entry->hash_node,
nfqnl_rhashtable_params);
if (unlikely(err))
return err;
@@ -266,23 +233,19 @@ __enqueue_entry(struct nfqnl_instance *queue, struct nf_queue_entry *entry)
static void
__dequeue_entry(struct nfqnl_instance *queue, struct nf_queue_entry *entry)
{
- rhashtable_remove_fast(&nfqnl_packet_map, &entry->hash_node,
+ rhashtable_remove_fast(&queue->nfqnl_packet_map, &entry->hash_node,
nfqnl_rhashtable_params);
list_del(&entry->list);
queue->queue_total--;
}

static struct nf_queue_entry *
-find_dequeue_entry(struct nfqnl_instance *queue, unsigned int id,
- struct net *net)
+find_dequeue_entry(struct nfqnl_instance *queue, unsigned int id)
{
- struct nfqnl_packet_key key;
struct nf_queue_entry *entry;

- nfqnl_init_key(&key, net, id, queue->queue_num);
-
spin_lock_bh(&queue->lock);
- entry = rhashtable_lookup_fast(&nfqnl_packet_map, &key,
+ entry = rhashtable_lookup_fast(&queue->nfqnl_packet_map, &id,
nfqnl_rhashtable_params);

if (entry)
@@ -1531,7 +1494,7 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,

verdict = ntohl(vhdr->verdict);

- entry = find_dequeue_entry(queue, ntohl(vhdr->id), info->net);
+ entry = find_dequeue_entry(queue, ntohl(vhdr->id));
if (entry == NULL)
return -ENOENT;

@@ -1880,40 +1843,38 @@ static int __init nfnetlink_queue_init(void)
{
int status;

- status = rhashtable_init(&nfqnl_packet_map, &nfqnl_rhashtable_params);
- if (status < 0)
- return status;
+ nfq_cleanup_wq = alloc_ordered_workqueue("nfq_workqueue", 0);
+ if (!nfq_cleanup_wq)
+ return -ENOMEM;

status = register_pernet_subsys(&nfnl_queue_net_ops);
- if (status < 0) {
- pr_err("failed to register pernet ops\n");
- goto cleanup_rhashtable;
- }
+ if (status < 0)
+ goto cleanup_pernet_subsys;

- netlink_register_notifier(&nfqnl_rtnl_notifier);
- status = nfnetlink_subsys_register(&nfqnl_subsys);
- if (status < 0) {
- pr_err("failed to create netlink socket\n");
- goto cleanup_netlink_notifier;
- }
+ status = netlink_register_notifier(&nfqnl_rtnl_notifier);
+ if (status < 0)
+ goto cleanup_rtnl_notifier;

status = register_netdevice_notifier(&nfqnl_dev_notifier);
- if (status < 0) {
- pr_err("failed to register netdevice notifier\n");
- goto cleanup_netlink_subsys;
- }
+ if (status < 0)
+ goto cleanup_dev_notifier;
+
+ status = nfnetlink_subsys_register(&nfqnl_subsys);
+ if (status < 0)
+ goto cleanup_nfqnl_subsys;

nf_register_queue_handler(&nfqh);

return status;

-cleanup_netlink_subsys:
- nfnetlink_subsys_unregister(&nfqnl_subsys);
-cleanup_netlink_notifier:
+cleanup_nfqnl_subsys:
+ unregister_netdevice_notifier(&nfqnl_dev_notifier);
+cleanup_dev_notifier:
netlink_unregister_notifier(&nfqnl_rtnl_notifier);
+cleanup_rtnl_notifier:
unregister_pernet_subsys(&nfnl_queue_net_ops);
-cleanup_rhashtable:
- rhashtable_destroy(&nfqnl_packet_map);
+cleanup_pernet_subsys:
+ destroy_workqueue(nfq_cleanup_wq);
return status;
}

@@ -1924,9 +1885,7 @@ static void __exit nfnetlink_queue_fini(void)
nfnetlink_subsys_unregister(&nfqnl_subsys);
netlink_unregister_notifier(&nfqnl_rtnl_notifier);
unregister_pernet_subsys(&nfnl_queue_net_ops);
-
- rhashtable_destroy(&nfqnl_packet_map);
-
+ destroy_workqueue(nfq_cleanup_wq);
rcu_barrier(); /* Wait for completion of call_rcu()'s */
}

--
2.53.0