[PATCH net 08/11] netfilter: nft_ct: drop pending enqueued packets on removal

[Florian Westphal <fw@strlen.de>]

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

Packets sitting in nfqueue might hold a reference to:

- templates that specify the conntrack zone, because a percpu area is
  used and module removal is possible.
- conntrack timeout policies and helper, where object removal leave
  a stale reference.

Since these objects can just go away, drop enqueued packets to avoid
stale reference to them.

If there is a need for finer grain removal, this logic can be revisited
to make selective packet drop upon dependencies.

Fixes: 7e0b2b57f01d ("netfilter: nft_ct: add ct timeout support")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nft_ct.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index 47d3ef109a99..128ff8155b5d 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -23,6 +23,7 @@
 #include <net/netfilter/nf_conntrack_l4proto.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 #include <net/netfilter/nf_conntrack_seqadj.h>
+#include "nf_internals.h"
 
 struct nft_ct_helper_obj  {
 	struct nf_conntrack_helper *helper4;
@@ -543,6 +544,7 @@ static void __nft_ct_set_destroy(const struct nft_ctx *ctx, struct nft_ct *priv)
 #endif
 #ifdef CONFIG_NF_CONNTRACK_ZONES
 	case NFT_CT_ZONE:
+		nf_queue_nf_hook_drop(ctx->net);
 		mutex_lock(&nft_ct_pcpu_mutex);
 		if (--nft_ct_pcpu_template_refcnt == 0)
 			nft_ct_tmpl_put_pcpu();
@@ -1015,6 +1017,7 @@ static void nft_ct_timeout_obj_destroy(const struct nft_ctx *ctx,
 	struct nft_ct_timeout_obj *priv = nft_obj_data(obj);
 	struct nf_ct_timeout *timeout = priv->timeout;
 
+	nf_queue_nf_hook_drop(ctx->net);
 	nf_ct_untimeout(ctx->net, timeout);
 	nf_ct_netns_put(ctx->net, ctx->family);
 	kfree(priv->timeout);
@@ -1147,6 +1150,7 @@ static void nft_ct_helper_obj_destroy(const struct nft_ctx *ctx,
 {
 	struct nft_ct_helper_obj *priv = nft_obj_data(obj);
 
+	nf_queue_nf_hook_drop(ctx->net);
 	if (priv->helper4)
 		nf_conntrack_helper_put(priv->helper4);
 	if (priv->helper6)
-- 
2.52.0