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authorCong Wang <xiyou.wangcong@gmail.com>2018-02-07 21:59:17 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-15 10:56:56 +0100
commitcbd6bb0e28c9c9772bd818fc7be1bb1452f3cf54 (patch)
parentec6b058c5431e7e1686c4d7ef42f951473baa78b (diff)
netfilter: ipt_CLUSTERIP: fix a race condition of proc file creation
commit b3e456fce9f51d6276e576d00271e2813c1b8b67 upstream. 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/' 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: 6c5d5cfbe3c5 ("netfilter: ipt_CLUSTERIP: check duplicate config when initializing") Tested-by: Paolo Abeni <pabeni@redhat.com> Cc: Xin Long <lucien.xin@gmail.com> Cc: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Reviewed-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 6 insertions, 6 deletions
diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 1e4a7209a3d2..77a01c484807 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -107,12 +107,6 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c)
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)
+ list_del_rcu(&c->list);
+ spin_unlock(&cn->lock);
+ local_bh_enable();
+ unregister_netdevice_notifier(&c->notifier);