netfilter: nf_tables: fix GC transaction races with netns and netlink event exit...

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>
(cherry picked from commit 6a33d8b73dfac0a41f3877894b38082bd0c9a5bc)
CVE-2023-4244
[cengizcan: fixes the fix commit]
Signed-off-by: Cengiz Can <cengiz.can@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 60c4c1f2c8f57f86070b0736343ad427e21af7b2..9aae076cf3a60ab1ab78d14d39ce505c2ac80bd8 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9454,6 +9454,22 @@ static void nft_set_commit_update(struct list_head *set_update_list)
        }
 }
 
+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 = nft_pernet(net);
@@ -9539,9 +9555,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
 
        WRITE_ONCE(nft_net->base_seq, base_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);
+       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);
@@ -9732,7 +9746,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
        nf_tables_gen_notify(net, skb, NFT_MSG_NEWGEN);
        nf_tables_commit_audit_log(&adl, nft_net->base_seq);
 
-       WRITE_ONCE(nft_net->gc_seq, ++gc_seq);
+       nft_gc_seq_end(nft_net, gc_seq);
        nf_tables_commit_release(net);
 
        return 0;
@@ -10714,6 +10728,7 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event,
        struct net *net = n->net;
        unsigned int deleted;
        bool restart = false;
+       unsigned int gc_seq;
 
        if (event != NETLINK_URELEASE || n->protocol != NETLINK_NETFILTER)
                return NOTIFY_DONE;
@@ -10721,6 +10736,9 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event,
        nft_net = nft_pernet(net);
        deleted = 0;
        mutex_lock(&nft_net->commit_mutex);
+
+       gc_seq = nft_gc_seq_begin(nft_net);
+
        if (!list_empty(&nf_tables_destroy_list))
                rcu_barrier();
 again:
@@ -10743,6 +10761,8 @@ again:
                if (restart)
                        goto again;
        }
+       nft_gc_seq_end(nft_net, gc_seq);
+
        mutex_unlock(&nft_net->commit_mutex);
 
        return NOTIFY_DONE;
@@ -10781,12 +10801,20 @@ static void __net_exit nf_tables_pre_exit_net(struct net *net)
 static void __net_exit nf_tables_exit_net(struct net *net)
 {
        struct nftables_pernet *nft_net = nft_pernet(net);
+       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) ||
            !list_empty(&nft_net->module_list))
                __nf_tables_abort(net, NFNL_ABORT_NONE);
+
        __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));
        WARN_ON_ONCE(!list_empty(&nft_net->module_list));