[PATCH -stable,4.19.x 13/40] netfilter: nf_tables: fix GC transaction races with netns and netlink event exit path

Pablo Neira Ayuso
2024-06-13T01:02:26Z

commit 6a33d8b73dfac0a41f3877894b38082bd0c9a5bc upstream.

Netlink event path is missing a synchronization point with GC
transactions. Add GC sequence number update to netns release path and
netlink event path, any GC transaction losing race will be discarded.

Fixes: 5f68718b34a5 ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
net/netfilter/nf_tables_api.c | 30 ++++++++++++++++++++++++++----
1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index aea8063f056d..4ac923ec11d6 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -6899,6 +6899,22 @@ void nft_trans_gc_queue_sync_done(struct nft_trans_gc *trans)
}
EXPORT_SYMBOL_GPL(nft_trans_gc_queue_sync_done);

+static unsigned int nft_gc_seq_begin(struct nftables_pernet *nft_net)
+{
+ unsigned int gc_seq;
+
+ /* Bump gc counter, it becomes odd, this is the busy mark. */
+ gc_seq = READ_ONCE(nft_net->gc_seq);
+ WRITE_ONCE(nft_net->gc_seq, ++gc_seq);
+
+ return gc_seq;
+}
+
+static void nft_gc_seq_end(struct nftables_pernet *nft_net, unsigned int gc_seq)
+{
+ WRITE_ONCE(nft_net->gc_seq, ++gc_seq);
+}
+
static int nf_tables_commit(struct net *net, struct sk_buff *skb)
{
struct nftables_pernet *nft_net = net_generic(net, nf_tables_net_id);
@@ -6953,9 +6969,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
while (++nft_net->base_seq == 0)
;

- /* Bump gc counter, it becomes odd, this is the busy mark. */
- gc_seq = READ_ONCE(nft_net->gc_seq);
- WRITE_ONCE(nft_net->gc_seq, ++gc_seq);
+ gc_seq = nft_gc_seq_begin(nft_net);

/* step 3. Start new generation, rules_gen_X now in use. */
net->nft.gencursor = nft_gencursor_next(net);
@@ -7083,7 +7097,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
nf_tables_commit_release(net);
nf_tables_gen_notify(net, skb, NFT_MSG_NEWGEN);

- WRITE_ONCE(nft_net->gc_seq, ++gc_seq);
+ nft_gc_seq_end(nft_net, gc_seq);
mutex_unlock(&nft_net->commit_mutex);

return 0;
@@ -7898,11 +7912,19 @@ static int __net_init nf_tables_init_net(struct net *net)
static void __net_exit nf_tables_exit_net(struct net *net)
{
struct nftables_pernet *nft_net = net_generic(net, nf_tables_net_id);
+ unsigned int gc_seq;

mutex_lock(&nft_net->commit_mutex);
+
+ gc_seq = nft_gc_seq_begin(nft_net);
+
if (!list_empty(&nft_net->commit_list))
__nf_tables_abort(net);
+
__nft_release_tables(net);
+
+ nft_gc_seq_end(nft_net, gc_seq);
+
mutex_unlock(&nft_net->commit_mutex);
WARN_ON_ONCE(!list_empty(&nft_net->tables));
}
--
2.30.2