5.4-stable review patch. If anyone has any objections, please let me know.
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From: Pablo Neira Ayuso pablo@netfilter.org
commit c03d278fdf35e73dd0ec543b9b556876b9d9a8dc upstream.
8c873e219970 ("netfilter: core: free hooks with call_rcu") removed synchronize_net() call when unregistering basechain hook, however, net_device removal event handler for the NFPROTO_NETDEV was not updated to wait for RCU grace period.
Note that 835b803377f5 ("netfilter: nf_tables_netdev: unregister hooks on net_device removal") does not remove basechain rules on device removal, I was hinted to remove rules on net_device removal later, see 5ebe0b0eec9d ("netfilter: nf_tables: destroy basechain and rules on netdevice removal").
Although NETDEV_UNREGISTER event is guaranteed to be handled after synchronize_net() call, this path needs to wait for rcu grace period via rcu callback to release basechain hooks if netns is alive because an ongoing netlink dump could be in progress (sockets hold a reference on the netns).
Note that nf_tables_pre_exit_net() unregisters and releases basechain hooks but it is possible to see NETDEV_UNREGISTER at a later stage in the netns exit path, eg. veth peer device in another netns:
cleanup_net() default_device_exit_batch() unregister_netdevice_many_notify() notifier_call_chain() nf_tables_netdev_event() __nft_release_basechain()
In this particular case, same rule of thumb applies: if netns is alive, then wait for rcu grace period because netlink dump in the other netns could be in progress. Otherwise, if the other netns is going away then no netlink dump can be in progress and basechain hooks can be released inmediately.
While at it, turn WARN_ON() into WARN_ON_ONCE() for the basechain validation, which should not ever happen.
Fixes: 835b803377f5 ("netfilter: nf_tables_netdev: unregister hooks on net_device removal") Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/netfilter/nf_tables.h | 3 ++ net/netfilter/nf_tables_api.c | 41 +++++++++++++++++++++++++++++++------- 2 files changed, 37 insertions(+), 7 deletions(-)
--- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -899,6 +899,7 @@ struct nft_chain { u8 flags:6, genmask:2; char *name; + struct rcu_head rcu_head;
/* Only used during control plane commit phase: */ struct nft_rule **rules_next; @@ -1015,6 +1016,7 @@ static inline void nft_use_inc_restore(u * @sets: sets in the table * @objects: stateful objects in the table * @flowtables: flow tables in the table + * @net: netnamespace this table belongs to * @hgenerator: handle generator state * @handle: table handle * @use: number of chain references to this table @@ -1030,6 +1032,7 @@ struct nft_table { struct list_head sets; struct list_head objects; struct list_head flowtables; + possible_net_t net; u64 hgenerator; u64 handle; u32 use; --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -1109,6 +1109,7 @@ static int nf_tables_newtable(struct net INIT_LIST_HEAD(&table->sets); INIT_LIST_HEAD(&table->objects); INIT_LIST_HEAD(&table->flowtables); + write_pnet(&table->net, net); table->family = family; table->flags = flags; table->handle = ++table_handle; @@ -8216,22 +8217,48 @@ int nft_data_dump(struct sk_buff *skb, i } EXPORT_SYMBOL_GPL(nft_data_dump);
-int __nft_release_basechain(struct nft_ctx *ctx) +static void __nft_release_basechain_now(struct nft_ctx *ctx) { struct nft_rule *rule, *nr;
- if (WARN_ON(!nft_is_base_chain(ctx->chain))) - return 0; - - nf_tables_unregister_hook(ctx->net, ctx->chain->table, ctx->chain); list_for_each_entry_safe(rule, nr, &ctx->chain->rules, list) { list_del(&rule->list); - nft_use_dec(&ctx->chain->use); nf_tables_rule_release(ctx, rule); } + nf_tables_chain_destroy(ctx->chain); +} + +static void nft_release_basechain_rcu(struct rcu_head *head) +{ + struct nft_chain *chain = container_of(head, struct nft_chain, rcu_head); + struct nft_ctx ctx = { + .family = chain->table->family, + .chain = chain, + .net = read_pnet(&chain->table->net), + }; + + __nft_release_basechain_now(&ctx); + put_net(ctx.net); +} + +int __nft_release_basechain(struct nft_ctx *ctx) +{ + struct nft_rule *rule; + + if (WARN_ON_ONCE(!nft_is_base_chain(ctx->chain))) + return 0; + + nf_tables_unregister_hook(ctx->net, ctx->chain->table, ctx->chain); + list_for_each_entry(rule, &ctx->chain->rules, list) + nft_use_dec(&ctx->chain->use); + nft_chain_del(ctx->chain); nft_use_dec(&ctx->table->use); - nf_tables_chain_destroy(ctx->chain); + + if (maybe_get_net(ctx->net)) + call_rcu(&ctx->chain->rcu_head, nft_release_basechain_rcu); + else + __nft_release_basechain_now(ctx);
return 0; }