[PATCH net 2/2] inet_diag: request _diag module only when the proto has been registered

[Xin Long]

The patch 'sock_diag: request _diag module only when the family has
been registered' fixed a security issue for sock_diag, the same fix
is needed for inet_diag module when requesting _diag module.

Fixes: 305e1e969114 ("[INET]: Let inet_diag and friends autoload")
Reported-by: Sabrina Dubroca <s...@queasysnail.net>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 include/net/protocol.h | 1 +
 net/ipv4/inet_diag.c   | 3 ++-
 net/ipv4/protocol.c    | 6 ++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/net/protocol.h b/include/net/protocol.h
index 4fc75f7..bf0dcc2 100644
--- a/include/net/protocol.h
+++ b/include/net/protocol.h
@@ -103,6 +103,7 @@ extern struct inet6_protocol __rcu 
*inet6_protos[MAX_INET_PROTOS];
 
 int inet_add_protocol(const struct net_protocol *prot, unsigned char num);
 int inet_del_protocol(const struct net_protocol *prot, unsigned char num);
+bool inet_proto_is_added(unsigned char num);
 int inet_add_offload(const struct net_offload *prot, unsigned char num);
 int inet_del_offload(const struct net_offload *prot, unsigned char num);
 void inet_register_protosw(struct inet_protosw *p);
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index c9c35b6..1460031 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -27,6 +27,7 @@
 #include <net/inet_hashtables.h>
 #include <net/inet_timewait_sock.h>
 #include <net/inet6_hashtables.h>
+#include <net/protocol.h>
 #include <net/netlink.h>
 
 #include <linux/inet.h>
@@ -52,7 +53,7 @@ static DEFINE_MUTEX(inet_diag_table_mutex);
 
 static const struct inet_diag_handler *inet_diag_lock_handler(int proto)
 {
-       if (!inet_diag_table[proto])
+       if (!inet_diag_table[proto] && inet_proto_is_added(proto))
                request_module("net-pf-%d-proto-%d-type-%d-%d", PF_NETLINK,
                               NETLINK_SOCK_DIAG, AF_INET, proto);
 
diff --git a/net/ipv4/protocol.c b/net/ipv4/protocol.c
index 32a691b..183386a 100644
--- a/net/ipv4/protocol.c
+++ b/net/ipv4/protocol.c
@@ -77,3 +77,9 @@ int inet_del_offload(const struct net_offload *prot, unsigned 
char protocol)
        return ret;
 }
 EXPORT_SYMBOL(inet_del_offload);
+
+bool inet_proto_is_added(unsigned char protocol)
+{
+       return !!rcu_access_pointer(inet_protos[protocol]);
+}
+EXPORT_SYMBOL(inet_proto_is_added);
-- 
2.1.0