From 933bd83ed60e80ebb1aeb64a2f7cd3190d2312e2 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 24 Apr 2017 15:37:39 +0200 Subject: [PATCH] netfilter: batch synchronize_net calls during hook unregister synchronize_net is expensive and slows down netns cleanup a lot. We have two APIs to unregister a hook: nf_unregister_net_hook (which calls synchronize_net()) and nf_unregister_net_hooks (calls nf_unregister_net_hook in a loop) Make nf_unregister_net_hook a wapper around new helper __nf_unregister_net_hook, which unlinks the hook but does not free it. Then, we can call that helper in nf_unregister_net_hooks and then call synchronize_net() only once. Andrey Konovalov reports this change improves syzkaller fuzzing speed at least twice. Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/core.c | 46 ++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 40 insertions(+), 6 deletions(-) diff --git a/net/netfilter/core.c b/net/netfilter/core.c index a87a6f8..b5d90885 100644 --- a/net/netfilter/core.c +++ b/net/netfilter/core.c @@ -126,14 +126,15 @@ int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg) } EXPORT_SYMBOL(nf_register_net_hook); -void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg) +static struct nf_hook_entry * +__nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg) { struct nf_hook_entry __rcu **pp; struct nf_hook_entry *p; pp = nf_hook_entry_head(net, reg); if (WARN_ON_ONCE(!pp)) - return; + return NULL; mutex_lock(&nf_hook_mutex); for (; (p = nf_entry_dereference(*pp)) != NULL; pp = &p->next) { @@ -145,7 +146,7 @@ void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg) mutex_unlock(&nf_hook_mutex); if (!p) { WARN(1, "nf_unregister_net_hook: hook not found!\n"); - return; + return NULL; } #ifdef CONFIG_NETFILTER_INGRESS if (reg->pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS) @@ -154,6 +155,17 @@ void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg) #ifdef HAVE_JUMP_LABEL static_key_slow_dec(&nf_hooks_needed[reg->pf][reg->hooknum]); #endif + + return p; +} + +void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg) +{ + struct nf_hook_entry *p = __nf_unregister_net_hook(net, reg); + + if (!p) + return; + synchronize_net(); nf_queue_nf_hook_drop(net, p); /* other cpu might still process nfqueue verdict that used reg */ @@ -183,10 +195,32 @@ err: EXPORT_SYMBOL(nf_register_net_hooks); void nf_unregister_net_hooks(struct net *net, const struct nf_hook_ops *reg, - unsigned int n) + unsigned int hookcount) { - while (n-- > 0) - nf_unregister_net_hook(net, ®[n]); + struct nf_hook_entry *to_free[16]; + unsigned int i, n; + + do { + n = min_t(unsigned int, hookcount, ARRAY_SIZE(to_free)); + + for (i = 0; i < n; i++) + to_free[i] = __nf_unregister_net_hook(net, ®[i]); + + synchronize_net(); + + for (i = 0; i < n; i++) { + if (to_free[i]) + nf_queue_nf_hook_drop(net, to_free[i]); + } + + synchronize_net(); + + for (i = 0; i < n; i++) + kfree(to_free[i]); + + reg += n; + hookcount -= n; + } while (hookcount > 0); } EXPORT_SYMBOL(nf_unregister_net_hooks); -- 2.7.4