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

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: 5f68718b34 ("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>
This commit is contained in:
Pablo Neira Ayuso 2023-08-15 15:39:00 +02:00 committed by Florian Westphal
parent 5310760af1
commit 6a33d8b73d
1 changed files with 32 additions and 4 deletions
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36
net/netfilter/nf_tables_api.c
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@ -9739,6 +9739,22 @@ 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);
@ -9824,9 +9840,7 @@ 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);
@ -10039,7 +10053,7 @@ 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;
@ -11040,6 +11054,7 @@ 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;
@ -11047,6 +11062,9 @@ 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:
@ -11069,6 +11087,8 @@ again:
if (restart)
goto again;
}
nft_gc_seq_end(nft_net, gc_seq);
mutex_unlock(&nft_net->commit_mutex);
return NOTIFY_DONE;
@ -11106,12 +11126,20 @@ 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));