Commit b3e456fc authored by Cong Wang's avatar Cong Wang Committed by Pablo Neira Ayuso

netfilter: ipt_CLUSTERIP: fix a race condition of proc file creation

There is a race condition between clusterip_config_entry_put()
and clusterip_config_init(), after we release the spinlock in
clusterip_config_entry_put(), a new proc file with a same IP could
be created immediately since it is already removed from the configs
list, therefore it triggers this warning:

------------[ cut here ]------------
proc_dir_entry 'ipt_CLUSTERIP/172.20.0.170' already registered
WARNING: CPU: 1 PID: 4152 at fs/proc/generic.c:330 proc_register+0x2a4/0x370 fs/proc/generic.c:329
Kernel panic - not syncing: panic_on_warn set ...

As a quick fix, just move the proc_remove() inside the spinlock.

Reported-by: <syzbot+03218bcdba6aa76441a3@syzkaller.appspotmail.com>
Fixes: 6c5d5cfb ("netfilter: ipt_CLUSTERIP: check duplicate config when initializing")
Tested-by: 's avatarPaolo Abeni <pabeni@redhat.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: 's avatarCong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: 's avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: 's avatarPablo Neira Ayuso <pablo@netfilter.org>
parent fd2c19b2
......@@ -107,12 +107,6 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
local_bh_disable();
if (refcount_dec_and_lock(&c->entries, &cn->lock)) {
list_del_rcu(&c->list);
spin_unlock(&cn->lock);
local_bh_enable();
unregister_netdevice_notifier(&c->notifier);
/* In case anyone still accesses the file, the open/close
* functions are also incrementing the refcount on their own,
* so it's safe to remove the entry even if it's in use. */
......@@ -120,6 +114,12 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
if (cn->procdir)
proc_remove(c->pde);
#endif
list_del_rcu(&c->list);
spin_unlock(&cn->lock);
local_bh_enable();
unregister_netdevice_notifier(&c->notifier);
return;
}
local_bh_enable();
......
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