[PATCH nf] netfilter: nfnetlink_cttimeout: nf_proto_net must be first member of netns_proto_gre

[Florian Westphal <fw@xxxxxxxxx>]

Can't move timeouts around, it appears conntrack sysctl unregister
assumes net_generic() returns nf_proto_net, so we get crash.

Expose layout of netns_proto_gre instead.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Fixes: 991acf532b  netfilter: nfnetlink_cttimeout: fetch timeouts for udplite and gre, too
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
 include/linux/netfilter/nf_conntrack_proto_gre.h | 13 +++++++++++++
 net/netfilter/nf_conntrack_proto_gre.c           | 14 +-------------
 net/netfilter/nfnetlink_cttimeout.c              |  8 ++++++--
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/include/linux/netfilter/nf_conntrack_proto_gre.h b/include/linux/netfilter/nf_conntrack_proto_gre.h
index b8d95564bd53..14edb795ab43 100644
--- a/include/linux/netfilter/nf_conntrack_proto_gre.h
+++ b/include/linux/netfilter/nf_conntrack_proto_gre.h
@@ -21,6 +21,19 @@ struct nf_ct_gre_keymap {
 	struct nf_conntrack_tuple tuple;
 };
 
+enum grep_conntrack {
+	GRE_CT_UNREPLIED,
+	GRE_CT_REPLIED,
+	GRE_CT_MAX
+};
+
+struct netns_proto_gre {
+	struct nf_proto_net	nf;
+	rwlock_t		keymap_lock;
+	struct list_head	keymap_list;
+	unsigned int		gre_timeouts[GRE_CT_MAX];
+};
+
 /* add new tuple->key_reply pair to keymap */
 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 			 struct nf_conntrack_tuple *t);
diff --git a/net/netfilter/nf_conntrack_proto_gre.c b/net/netfilter/nf_conntrack_proto_gre.c
index dd8db7fbc437..2a5e56c6d8d9 100644
--- a/net/netfilter/nf_conntrack_proto_gre.c
+++ b/net/netfilter/nf_conntrack_proto_gre.c
@@ -43,24 +43,12 @@
 #include <linux/netfilter/nf_conntrack_proto_gre.h>
 #include <linux/netfilter/nf_conntrack_pptp.h>
 
-enum grep_conntrack {
-	GRE_CT_UNREPLIED,
-	GRE_CT_REPLIED,
-	GRE_CT_MAX
-};
-
 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
 	[GRE_CT_UNREPLIED]	= 30*HZ,
 	[GRE_CT_REPLIED]	= 180*HZ,
 };
 
 static unsigned int proto_gre_net_id __read_mostly;
-struct netns_proto_gre {
-	unsigned int		gre_timeouts[GRE_CT_MAX];
-	struct nf_proto_net	nf;
-	rwlock_t		keymap_lock;
-	struct list_head	keymap_list;
-};
 
 static inline struct netns_proto_gre *gre_pernet(struct net *net)
 {
@@ -402,7 +390,7 @@ static int __init nf_ct_proto_gre_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(offsetof(struct netns_proto_gre, gre_timeouts));
+	BUILD_BUG_ON(offsetof(struct netns_proto_gre, nf) != 0);
 
 	ret = register_pernet_subsys(&proto_gre_net_ops);
 	if (ret < 0)
diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c
index 1643faa35f56..109b0d27345a 100644
--- a/net/netfilter/nfnetlink_cttimeout.c
+++ b/net/netfilter/nfnetlink_cttimeout.c
@@ -474,8 +474,12 @@ static int cttimeout_default_get(struct net *net, struct sock *ctnl,
 		break;
 	case IPPROTO_GRE:
 #ifdef CONFIG_NF_CT_PROTO_GRE
-		if (l4proto->net_id)
-			timeouts = net_generic(net, *l4proto->net_id);
+		if (l4proto->net_id) {
+			struct netns_proto_gre *net_gre;
+
+			net_gre = net_generic(net, *l4proto->net_id);
+			timeouts = net_gre->gre_timeouts;
+		}
 #endif
 		break;
 	case 255:
-- 
2.18.1