[PATCH net] sock_diag: request _diag module only when the family or proto has been registered
From: Xin Long <lucien.xin@gmail.com>
Date: 2017-10-17 05:14:05
Now when using 'ss' in iproute, kernel would try to load all _diag modules. It causes the corresponding family or proto modules to be loaded as well. Like after 'ss -a', sctp, dccp, af_packet(if it works as a moudle) will be loaded. As these family or proto modules are loaded unexpectly, this might have some security implications. This patch is to introduce sock_diag_request_module() in which we only request the _diag module when it's corresponding family or proto has been registered. Note that we can't just load _diag module without the family or proto loaded, as some symbols in _diag module are from the family or proto moudle. Reported-by: Sabrina Dubroca <sd@queasysnail.net> Signed-off-by: Xin Long <lucien.xin@gmail.com> --- include/linux/net.h | 1 + include/linux/sock_diag.h | 1 + net/core/sock_diag.c | 32 ++++++++++++++++++++++++-------- net/ipv4/inet_diag.c | 3 +-- net/socket.c | 5 +++++ 5 files changed, 32 insertions(+), 10 deletions(-)
diff --git a/include/linux/net.h b/include/linux/net.h
index d97d80d..6c7cf09 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h@@ -225,6 +225,7 @@ enum { int sock_wake_async(struct socket_wq *sk_wq, int how, int band); int sock_register(const struct net_proto_family *fam); void sock_unregister(int family); +bool sock_is_registered(int family); int __sock_create(struct net *net, int family, int type, int proto, struct socket **res, int kern); int sock_create(int family, int type, int proto, struct socket **res);
diff --git a/include/linux/sock_diag.h b/include/linux/sock_diag.h
index a2f8109..e9a1b8d 100644
--- a/include/linux/sock_diag.h
+++ b/include/linux/sock_diag.h@@ -77,4 +77,5 @@ bool sock_diag_has_destroy_listeners(const struct sock *sk) void sock_diag_broadcast_destroy(struct sock *sk); int sock_diag_destroy(struct sock *sk, int err); +int sock_diag_request_module(int family, int protocol); #endif
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index 217f4e3..caad6b6 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c@@ -7,6 +7,7 @@ #include <net/net_namespace.h> #include <linux/module.h> #include <net/sock.h> +#include <net/protocol.h> #include <linux/kernel.h> #include <linux/tcp.h> #include <linux/workqueue.h>
@@ -207,6 +208,25 @@ void sock_diag_unregister(const struct sock_diag_handler *hnld) } EXPORT_SYMBOL_GPL(sock_diag_unregister); +int sock_diag_request_module(int family, int protocol) +{ + if (!protocol) { + if (!sock_is_registered(family)) + return -ENOENT; + + return request_module("net-pf-%d-proto-%d-type-%d", PF_NETLINK, + NETLINK_SOCK_DIAG, family); + } + + if (family == AF_INET && + !rcu_access_pointer(inet_protos[protocol])) + return -ENOENT; + + return request_module("net-pf-%d-proto-%d-type-%d-%d", PF_NETLINK, + NETLINK_SOCK_DIAG, family, protocol); +} +EXPORT_SYMBOL_GPL(sock_diag_request_module); + static int __sock_diag_cmd(struct sk_buff *skb, struct nlmsghdr *nlh) { int err;
@@ -220,8 +240,7 @@ static int __sock_diag_cmd(struct sk_buff *skb, struct nlmsghdr *nlh) return -EINVAL; if (sock_diag_handlers[req->sdiag_family] == NULL) - request_module("net-pf-%d-proto-%d-type-%d", PF_NETLINK, - NETLINK_SOCK_DIAG, req->sdiag_family); + sock_diag_request_module(req->sdiag_family, 0); mutex_lock(&sock_diag_table_mutex); hndl = sock_diag_handlers[req->sdiag_family];
@@ -247,8 +266,7 @@ static int sock_diag_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, case TCPDIAG_GETSOCK: case DCCPDIAG_GETSOCK: if (inet_rcv_compat == NULL) - request_module("net-pf-%d-proto-%d-type-%d", PF_NETLINK, - NETLINK_SOCK_DIAG, AF_INET); + sock_diag_request_module(AF_INET, 0); mutex_lock(&sock_diag_table_mutex); if (inet_rcv_compat != NULL)
@@ -281,14 +299,12 @@ static int sock_diag_bind(struct net *net, int group) case SKNLGRP_INET_TCP_DESTROY: case SKNLGRP_INET_UDP_DESTROY: if (!sock_diag_handlers[AF_INET]) - request_module("net-pf-%d-proto-%d-type-%d", PF_NETLINK, - NETLINK_SOCK_DIAG, AF_INET); + sock_diag_request_module(AF_INET, 0); break; case SKNLGRP_INET6_TCP_DESTROY: case SKNLGRP_INET6_UDP_DESTROY: if (!sock_diag_handlers[AF_INET6]) - request_module("net-pf-%d-proto-%d-type-%d", PF_NETLINK, - NETLINK_SOCK_DIAG, AF_INET); + sock_diag_request_module(AF_INET, 0); break; } return 0;
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index c9c35b6..d10c8fa 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c@@ -53,8 +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]) - request_module("net-pf-%d-proto-%d-type-%d-%d", PF_NETLINK, - NETLINK_SOCK_DIAG, AF_INET, proto); + sock_diag_request_module(AF_INET, proto); mutex_lock(&inet_diag_table_mutex); if (!inet_diag_table[proto])
diff --git a/net/socket.c b/net/socket.c
index c729625..733d657 100644
--- a/net/socket.c
+++ b/net/socket.c@@ -2590,6 +2590,11 @@ void sock_unregister(int family) } EXPORT_SYMBOL(sock_unregister); +bool sock_is_registered(int family) +{ + return family < NPROTO && rcu_access_pointer(net_families[family]); +} + static int __init sock_init(void) { int err;
--
2.1.0