[PATCH 5.15 26/66] netfilter: nf_tables: double hook unregistration in netns path

Greg Kroah-Hartman
2022-06-03T17:58:28Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 54 +++++++++++++++++++++++++++++++-----------
1 file changed, 41 insertions(+), 13 deletions(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -222,12 +222,18 @@ err_register:
}

static void nft_netdev_unregister_hooks(struct net *net,
- struct list_head *hook_list)
+ struct list_head *hook_list,
+ bool release_netdev)
{
- struct nft_hook *hook;
+ struct nft_hook *hook, *next;

- list_for_each_entry(hook, hook_list, list)
+ list_for_each_entry_safe(hook, next, hook_list, list) {
nf_unregister_net_hook(net, &hook->ops);
+ if (release_netdev) {
+ list_del(&hook->list);
+ kfree_rcu(hook, rcu);
+ }
+ }
}

static int nf_tables_register_hook(struct net *net,
@@ -253,9 +259,10 @@ static int nf_tables_register_hook(struc
return nf_register_net_hook(net, &basechain->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)
{
struct nft_base_chain *basechain;
const struct nf_hook_ops *ops;
@@ -270,11 +277,19 @@ static void nf_tables_unregister_hook(st
return basechain->type->ops_unregister(net, ops);

if (nft_base_chain_netdev(table->family, basechain->ops.hooknum))
- nft_netdev_unregister_hooks(net, &basechain->hook_list);
+ nft_netdev_unregister_hooks(net, &basechain->hook_list,
+ release_netdev);
else
nf_unregister_net_hook(net, &basechain->ops);
}

+static void nf_tables_unregister_hook(struct net *net,
+ const struct nft_table *table,
+ struct nft_chain *chain)
+{
+ return __nf_tables_unregister_hook(net, table, chain, false);
+}
+
static void nft_trans_commit_list_add_tail(struct net *net, struct nft_trans *trans)
{
struct nftables_pernet *nft_net = nft_pernet(net);
@@ -7206,13 +7221,25 @@ static void nft_unregister_flowtable_hoo
FLOW_BLOCK_UNBIND);
}

-static void nft_unregister_flowtable_net_hooks(struct net *net,
- struct list_head *hook_list)
+static void __nft_unregister_flowtable_net_hooks(struct net *net,
+ struct list_head *hook_list,
+ bool release_netdev)
{
- struct nft_hook *hook;
+ struct nft_hook *hook, *next;

- list_for_each_entry(hook, hook_list, list)
+ list_for_each_entry_safe(hook, next, hook_list, list) {
nf_unregister_net_hook(net, &hook->ops);
+ if (release_netdev) {
+ list_del(&hook->list);
+ kfree_rcu(hook);
+ }
+ }
+}
+
+static void nft_unregister_flowtable_net_hooks(struct net *net,
+ struct list_head *hook_list)
+{
+ __nft_unregister_flowtable_net_hooks(net, hook_list, false);
}

static int nft_register_flowtable_net_hooks(struct net *net,
@@ -9605,9 +9632,10 @@ static void __nft_release_hook(struct ne
struct nft_chain *chain;

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->hook_list);
+ __nft_unregister_flowtable_net_hooks(net, &flowtable->hook_list,
+ true);
}

static void __nft_release_hooks(struct net *net)