[PATCH -stable,4.19.x 22/40] netfilter: nf_tables: double hook unregistration in netns path

Pablo Neira Ayuso
2024-06-13T01:02:32Z

commit f9a43007d3f7ba76d5e7f9421094f00f2ef202f8 upstream.

__nft_release_hooks() is called from pre_netns exit path which
unregisters the hooks, then the NETDEV_UNREGISTER event is triggered
which unregisters the hooks again.

[ 565.221461] WARNING: CPU: 18 PID: 193 at net/netfilter/core.c:495 __nf_unregister_net_hook+0x247/0x270
[...]
[ 565.246890] CPU: 18 PID: 193 Comm: kworker/u64:1 Tainted: G E 5.18.0-rc7+ #27
[ 565.253682] Workqueue: netns cleanup_net
[ 565.257059] RIP: 0010:__nf_unregister_net_hook+0x247/0x270
[...]
[ 565.297120] Call Trace:
[ 565.300900] <TASK>
[ 565.304683] nf_tables_flowtable_event+0x16a/0x220 [nf_tables]
[ 565.308518] raw_notifier_call_chain+0x63/0x80
[ 565.312386] unregister_netdevice_many+0x54f/0xb50

Unregister and destroy netdev hook from netns pre_exit via kfree_rcu
so the NETDEV_UNREGISTER path see unregistered hooks.

Fixes: 767d1216bff8 ("netfilter: nftables: fix possible UAF over chains from packet path in netns")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/nf_tables_api.c | 34 +++++++++++++++++++++++++-------
net/netfilter/nft_chain_filter.c | 3 +++
2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 719b30d6ec64..adab83a22f6c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -204,9 +204,10 @@ static int nf_tables_register_hook(struct net *net,
return nf_register_net_hook(net, ops);
}

-static void nf_tables_unregister_hook(struct net *net,
- const struct nft_table *table,
- struct nft_chain *chain)
+static void __nf_tables_unregister_hook(struct net *net,
+ const struct nft_table *table,
+ struct nft_chain *chain,
+ bool release_netdev)
{
const struct nft_base_chain *basechain;
const struct nf_hook_ops *ops;
@@ -221,6 +222,16 @@ static void nf_tables_unregister_hook(struct net *net,
return basechain->type->ops_unregister(net, ops);

nf_unregister_net_hook(net, ops);
+ if (release_netdev &&
+ table->family == NFPROTO_NETDEV)
+ nft_base_chain(chain)->ops.dev = NULL;
+}
+
+static void nf_tables_unregister_hook(struct net *net,
+ const struct nft_table *table,
+ struct nft_chain *chain)
+{
+ __nf_tables_unregister_hook(net, table, chain, false);
}

static int nft_trans_table_add(struct nft_ctx *ctx, int msg_type)
@@ -5821,8 +5832,9 @@ nft_flowtable_type_get(struct net *net, u8 family)
return ERR_PTR(-ENOENT);
}

-static void nft_unregister_flowtable_net_hooks(struct net *net,
- struct nft_flowtable *flowtable)
+static void __nft_unregister_flowtable_net_hooks(struct net *net,
+ struct nft_flowtable *flowtable,
+ bool release_netdev)
{
int i;

@@ -5831,9 +5843,17 @@ static void nft_unregister_flowtable_net_hooks(struct net *net,
continue;

nf_unregister_net_hook(net, &flowtable->ops[i]);
+ if (release_netdev)
+ flowtable->ops[i].dev = NULL;
}
}

+static void nft_unregister_flowtable_net_hooks(struct net *net,
+ struct nft_flowtable *flowtable)
+{
+ __nft_unregister_flowtable_net_hooks(net, flowtable, false);
+}
+
static int nf_tables_newflowtable(struct net *net, struct sock *nlsk,
struct sk_buff *skb,
const struct nlmsghdr *nlh,
@@ -7862,9 +7882,9 @@ static void __nft_release_table(struct net *net, struct nft_table *table)
ctx.family = table->family;

list_for_each_entry(chain, &table->chains, list)
- nf_tables_unregister_hook(net, table, chain);
+ __nf_tables_unregister_hook(net, table, chain, true);
list_for_each_entry(flowtable, &table->flowtables, list)
- nft_unregister_flowtable_net_hooks(net, flowtable);
+ __nft_unregister_flowtable_net_hooks(net, flowtable, true);
/* No packets are walking on these chains anymore. */
ctx.table = table;
list_for_each_entry(chain, &table->chains, list) {
diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
index a308d45ee95e..397aa83f54e0 100644
--- a/net/netfilter/nft_chain_filter.c
+++ b/net/netfilter/nft_chain_filter.c
@@ -296,6 +296,9 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev,
if (strcmp(basechain->dev_name, dev->name) != 0)
return;

+ if (!basechain->ops.dev)
+ return;
+
/* UNREGISTER events are also happpening on netns exit.
*
* Altough nf_tables core releases all tables/chains, only
--
2.30.2