From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xin Long Subject: Re: [Patch net] ipt_CLUSTERIP: fix a race condition of proc file creation Date: Thu, 8 Feb 2018 19:45:05 +0800 Message-ID: References: <20180208055918.20411-1-xiyou.wangcong@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: network dev , netfilter-devel@vger.kernel.org, Paolo Abeni , Pablo Neira Ayuso To: Cong Wang Return-path: In-Reply-To: <20180208055918.20411-1-xiyou.wangcong@gmail.com> Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org On Thu, Feb 8, 2018 at 1:59 PM, Cong Wang wrote: > 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: > Fixes: 6c5d5cfbe3c5 ("netfilter: ipt_CLUSTERIP: check duplicate config when initializing") > Tested-by: Paolo Abeni > Cc: Xin Long > Cc: Pablo Neira Ayuso > Signed-off-by: Cong Wang > --- > net/ipv4/netfilter/ipt_CLUSTERIP.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c > index 3a84a60f6b39..1ff72b87a066 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) > > 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(); > -- > 2.13.0 > Reviewed-by: Xin Long