[PATCH net] net: ping6: Fix possible leaked pernet namespace in pingv6_init()

[Chen Zhongjin]

When IPv6 module initializing in pingv6_init(), inet6_register_protosw()
is possible to fail but returns without any error cleanup.

This leaves wild ops in namespace list and when another module tries to
add or delete pernet namespace it triggers page fault.
Although IPv6 cannot be unloaded now, this error should still be handled
to avoid kernel panic during IPv6 initialization.

BUG: unable to handle page fault for address: fffffbfff80bab69
CPU: 0 PID: 434 Comm: modprobe
RIP: 0010:unregister_pernet_operations+0xc9/0x450
Call Trace:
 <TASK>
 unregister_pernet_subsys+0x31/0x3e
 nf_tables_module_exit+0x44/0x6a [nf_tables]
 __do_sys_delete_module.constprop.0+0x34f/0x5b0
 ...

Fix it by adding error handling in pingv6_init(), and add a helper
function pingv6_ops_unset to avoid duplicate code.

Fixes: d862e5461423 ("net: ipv6: Implement /proc/net/icmp6.")
Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
---
 net/ipv6/ping.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index 86c26e48d065..5df688dd5208 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -277,10 +277,21 @@ static struct pernet_operations ping_v6_net_ops = {
 };
 #endif
 
+static void pingv6_ops_unset(void)
+{
+	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
+	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
+	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
+	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
+	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
+	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
+}
+
 int __init pingv6_init(void)
 {
+	int ret;
 #ifdef CONFIG_PROC_FS
-	int ret = register_pernet_subsys(&ping_v6_net_ops);
+	ret = register_pernet_subsys(&ping_v6_net_ops);
 	if (ret)
 		return ret;
 #endif
@@ -291,7 +302,15 @@ int __init pingv6_init(void)
 	pingv6_ops.icmpv6_err_convert = icmpv6_err_convert;
 	pingv6_ops.ipv6_icmp_error = ipv6_icmp_error;
 	pingv6_ops.ipv6_chk_addr = ipv6_chk_addr;
-	return inet6_register_protosw(&pingv6_protosw);
+
+	ret = inet6_register_protosw(&pingv6_protosw);
+	if (ret) {
+		pingv6_ops_unset();
+#ifdef CONFIG_PROC_FS
+		unregister_pernet_subsys(&ping_v6_net_ops);
+#endif
+	}
+	return ret;
 }
 
 /* This never gets called because it's not possible to unload the ipv6 module,
@@ -299,12 +318,7 @@ int __init pingv6_init(void)
  */
 void pingv6_exit(void)
 {
-	pingv6_ops.ipv6_recv_error = dummy_ipv6_recv_error;
-	pingv6_ops.ip6_datagram_recv_common_ctl = dummy_ip6_datagram_recv_ctl;
-	pingv6_ops.ip6_datagram_recv_specific_ctl = dummy_ip6_datagram_recv_ctl;
-	pingv6_ops.icmpv6_err_convert = dummy_icmpv6_err_convert;
-	pingv6_ops.ipv6_icmp_error = dummy_ipv6_icmp_error;
-	pingv6_ops.ipv6_chk_addr = dummy_ipv6_chk_addr;
+	pingv6_ops_unset();
 #ifdef CONFIG_PROC_FS
 	unregister_pernet_subsys(&ping_v6_net_ops);
 #endif
-- 
2.17.1