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netfilter: ipt_CLUSTERIP: check duplicate config when initializing

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Now when adding an ipt_CLUSTERIP rule, it only checks duplicate config in
clusterip_config_find_get(). But after that, there may be still another
thread to insert a config with the same ip, then it leaves proc_create_data
to do duplicate check.

It's more reasonable to check duplicate config by ipt_CLUSTERIP itself,
instead of checking it by proc fs duplicate file check. Before, when proc
fs allowed duplicate name files in a directory, It could even crash kernel
because of use-after-free.

This patch is to check duplicate config under the protection of clusterip
net lock when initializing a new config and correct the return err.

Note that it also moves proc file node creation after adding new config, as
proc_create_data may sleep, it couldn't be called under the clusterip_net
lock. clusterip_config_find_get returns NULL if c->pde is null to make sure
it can't be used until the proc file node creation is done.

Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Xin Long 2016-12-20 19:14:34 +08:00 committed by Pablo Neira Ayuso
parent 053d20f571
commit 6c5d5cfbe3
1 changed files with 23 additions and 11 deletions
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34
net/ipv4/netfilter/ipt_CLUSTERIP.c
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@ -144,7 +144,7 @@ clusterip_config_find_get(struct net *net, __be32 clusterip, int entry)
rcu_read_lock_bh(); rcu_read_lock_bh();
c = __clusterip_config_find(net, clusterip); c = __clusterip_config_find(net, clusterip);
if (c) { if (c) {
if (unlikely(!atomic_inc_not_zero(&c->refcount))) if (!c->pde || unlikely(!atomic_inc_not_zero(&c->refcount)))
c = NULL; c = NULL;
else if (entry) else if (entry)
atomic_inc(&c->entries); atomic_inc(&c->entries);
@ -166,14 +166,15 @@ clusterip_config_init_nodelist(struct clusterip_config *c,
static struct clusterip_config * static struct clusterip_config *
clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip, clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
struct net_device *dev) struct net_device *dev)
{ {
struct net *net = dev_net(dev);
struct clusterip_config *c; struct clusterip_config *c;
struct clusterip_net *cn = net_generic(dev_net(dev), clusterip_net_id); struct clusterip_net *cn = net_generic(net, clusterip_net_id);
c = kzalloc(sizeof(*c), GFP_ATOMIC); c = kzalloc(sizeof(*c), GFP_ATOMIC);
if (!c) if (!c)
return NULL; return ERR_PTR(-ENOMEM);
c->dev = dev; c->dev = dev;
c->clusterip = ip; c->clusterip = ip;
@ -185,6 +186,17 @@ clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
atomic_set(&c->refcount, 1); atomic_set(&c->refcount, 1);
atomic_set(&c->entries, 1); atomic_set(&c->entries, 1);
spin_lock_bh(&cn->lock);
if (__clusterip_config_find(net, ip)) {
spin_unlock_bh(&cn->lock);
kfree(c);
return ERR_PTR(-EBUSY);
}
list_add_rcu(&c->list, &cn->configs);
spin_unlock_bh(&cn->lock);
#ifdef CONFIG_PROC_FS #ifdef CONFIG_PROC_FS
{ {
char buffer[16]; char buffer[16];
@ -195,16 +207,16 @@ clusterip_config_init(const struct ipt_clusterip_tgt_info *i, __be32 ip,
cn->procdir, cn->procdir,
&clusterip_proc_fops, c); &clusterip_proc_fops, c);
if (!c->pde) { if (!c->pde) {
spin_lock_bh(&cn->lock);
list_del_rcu(&c->list);
spin_unlock_bh(&cn->lock);
kfree(c); kfree(c);
return NULL;
return ERR_PTR(-ENOMEM);
} }
} }
#endif #endif
spin_lock_bh(&cn->lock);
list_add_rcu(&c->list, &cn->configs);
spin_unlock_bh(&cn->lock);
return c; return c;
} }
@ -410,9 +422,9 @@ static int clusterip_tg_check(const struct xt_tgchk_param *par)
config = clusterip_config_init(cipinfo, config = clusterip_config_init(cipinfo,
e->ip.dst.s_addr, dev); e->ip.dst.s_addr, dev);
if (!config) { if (IS_ERR(config)) {
dev_put(dev); dev_put(dev);
return -ENOMEM; return PTR_ERR(config);
} }
dev_mc_add(config->dev, config->clustermac); dev_mc_add(config->dev, config->clustermac);
} }