[PATCH net-next] ipv4: fix kfree static array pointer in ipv4_sysctl_exit_net

[Wang Weidong <wangweidong1@huawei.com>]

In ipv4_sysctl_init_net, we don't kmemdup a sysctl_table for init_net,
so init_net->ipv4.ipv4_hdr->ctl_table_arg points to ipv4_net_table which
is a static array pointer. So when do ipv4_sysctl_exit_net, it will
free the ipv4_net_table for init_net.

So add a check net_namespace init_net before kfree the sysctl_table.

Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
---
 net/ipv4/sysctl_net_ipv4.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 44eba05..2825577 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -891,7 +891,8 @@ static __net_exit void ipv4_sysctl_exit_net(struct net *net)
 
 	table = net->ipv4.ipv4_hdr->ctl_table_arg;
 	unregister_net_sysctl_table(net->ipv4.ipv4_hdr);
-	kfree(table);
+	if (!net_eq(net, &init_net))
+		kfree(table);
 }
 
 static __net_initdata struct pernet_operations ipv4_sysctl_ops = {
-- 
1.7.12