Hi Gao, On Fri, Dec 28, 2012 at 10:36:27AM +0800, Gao feng wrote: > canqun zhang reported a panic BUG,kernel may panic when > unloading nf_conntrack module. > > It's because we reset nf_ct_destroy to NULL when we deal > with init_net,it's too early.Some packets belongs to other > netns still refers to the conntrack.when these packets need > to be freed, kfree_skb will call nf_ct_destroy which is > NULL. > > fix this bug by moving the nf_conntrack initialize and cleanup > codes out of the pernet operations,this job should be done > in module_init/exit.We can't use init_net to identify if > it's the right time. First off, thanks for looking into this. I want to get this fix into 3.8 and -stable but this patch includes a rework whose scope is net-next (upcoming 3.9). The attached patch aims to fix the issue according to your patch description. Once this is in, we can revisit your code refactoring proposal. Let me know.
>From a211bd666fbfe17ae7171a50ad92fedc7b9e19fa Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> Date: Thu, 10 Jan 2013 16:12:01 +0100 Subject: [PATCH] netfilter: nf_conntrack: fix BUG_ON while removing nf_conntrack with netns canqun zhang reported that we're hitting BUG_ON in the nf_conntrack_destroy path when calling kfree_skb while rmmod'ing the nf_conntrack module. Currently, the nf_ct_destroy hook is being set to NULL in the destroy path of conntrack.init_net. However, this is a problem since init_net may be destroyed before any other existing netns (we cannot assume any specific ordering while releasing existing netns according to what I read in recent emails). Thanks to Gao feng for initial patch to address this issue. Reported-by: canqun zhang <canqunzhang@xxxxxxxxx> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> --- include/net/netfilter/nf_conntrack_core.h | 2 ++ net/netfilter/nf_conntrack_core.c | 9 +++++---- net/netfilter/nf_conntrack_standalone.c | 1 + 3 files changed, 8 insertions(+), 4 deletions(-) diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h index d8f5b9f..e98aeb3 100644 --- a/include/net/netfilter/nf_conntrack_core.h +++ b/include/net/netfilter/nf_conntrack_core.h @@ -31,6 +31,8 @@ extern void nf_conntrack_cleanup(struct net *net); extern int nf_conntrack_proto_init(struct net *net); extern void nf_conntrack_proto_fini(struct net *net); +extern void nf_conntrack_cleanup_end(void); + extern bool nf_ct_get_tuple(const struct sk_buff *skb, unsigned int nhoff, diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 016d95e..e4a0c4f 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -1376,11 +1376,12 @@ void nf_conntrack_cleanup(struct net *net) synchronize_net(); nf_conntrack_proto_fini(net); nf_conntrack_cleanup_net(net); +} - if (net_eq(net, &init_net)) { - RCU_INIT_POINTER(nf_ct_destroy, NULL); - nf_conntrack_cleanup_init_net(); - } +void nf_conntrack_cleanup_end(void) +{ + RCU_INIT_POINTER(nf_ct_destroy, NULL); + nf_conntrack_cleanup_init_net(); } void *nf_ct_alloc_hashtable(unsigned int *sizep, int nulls) diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c index 363285d..e7185c6 100644 --- a/net/netfilter/nf_conntrack_standalone.c +++ b/net/netfilter/nf_conntrack_standalone.c @@ -575,6 +575,7 @@ static int __init nf_conntrack_standalone_init(void) static void __exit nf_conntrack_standalone_fini(void) { unregister_pernet_subsys(&nf_conntrack_net_ops); + nf_conntrack_cleanup_end(); } module_init(nf_conntrack_standalone_init); -- 1.7.10.4