lwtunnel: fix autoload of lwt modules

Trying to add an mpls encap route when the MPLS modules are not loaded
hangs. For example:

    CONFIG_MPLS=y
    CONFIG_NET_MPLS_GSO=m
    CONFIG_MPLS_ROUTING=m
    CONFIG_MPLS_IPTUNNEL=m

    $ ip route add 10.10.10.10/32 encap mpls 100 via inet 10.100.1.2

The ip command hangs:
root       880   826  0 21:25 pts/0    00:00:00 ip route add 10.10.10.10/32 encap mpls 100 via inet 10.100.1.2

    $ cat /proc/880/stack
    [<ffffffff81065a9b>] call_usermodehelper_exec+0xd6/0x134
    [<ffffffff81065efc>] __request_module+0x27b/0x30a
    [<ffffffff814542f6>] lwtunnel_build_state+0xe4/0x178
    [<ffffffff814aa1e4>] fib_create_info+0x47f/0xdd4
    [<ffffffff814ae451>] fib_table_insert+0x90/0x41f
    [<ffffffff814a8010>] inet_rtm_newroute+0x4b/0x52
    ...

modprobe is trying to load rtnl-lwt-MPLS:

root       881     5  0 21:25 ?        00:00:00 /sbin/modprobe -q -- rtnl-lwt-MPLS

and it hangs after loading mpls_router:

    $ cat /proc/881/stack
    [<ffffffff81441537>] rtnl_lock+0x12/0x14
    [<ffffffff8142ca2a>] register_netdevice_notifier+0x16/0x179
    [<ffffffffa0033025>] mpls_init+0x25/0x1000 [mpls_router]
    [<ffffffff81000471>] do_one_initcall+0x8e/0x13f
    [<ffffffff81119961>] do_init_module+0x5a/0x1e5
    [<ffffffff810bd070>] load_module+0x13bd/0x17d6
    ...

The problem is that lwtunnel_build_state is called with rtnl lock
held preventing mpls_init from registering.

Given the potential references held by the time lwtunnel_build_state it
can not drop the rtnl lock to the load module. So, extract the module
loading code from lwtunnel_build_state into a new function to validate
the encap type. The new function is called while converting the user
request into a fib_config which is well before any table, device or
fib entries are examined.

Fixes: 745041e2aaf1 ("lwtunnel: autoload of lwt modules")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h
index d4c1c75b886244f76f9539c0709bb72be7974578..0b585f1fd340c12755d4eb9453671ea0c81e6507 100644 (file)
--- a/include/net/lwtunnel.h
+++ b/include/net/lwtunnel.h
@@ -105,6 +105,8 @@ int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *op,
                           unsigned int num);
 int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *op,
                           unsigned int num);
+int lwtunnel_valid_encap_type(u16 encap_type);
+int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int len);
 int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
                         struct nlattr *encap,
                         unsigned int family, const void *cfg,
@@ -168,6 +170,15 @@ static inline int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *op,
        return -EOPNOTSUPP;
 }
 
+static inline int lwtunnel_valid_encap_type(u16 encap_type)
+{
+       return -EOPNOTSUPP;
+}
+static inline int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int len)
+{
+       return -EOPNOTSUPP;
+}
+
 static inline int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
                                       struct nlattr *encap,
                                       unsigned int family, const void *cfg,

diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
index a5d4e866ce88b4d055798d9ea55fc905b351fb3d..47b1dd65947bd2547cf22a0bb84592fef8f28be0 100644 (file)
--- a/net/core/lwtunnel.c
+++ b/net/core/lwtunnel.c
@@ -26,6 +26,7 @@
 #include <net/lwtunnel.h>
 #include <net/rtnetlink.h>
 #include <net/ip6_fib.h>
+#include <net/nexthop.h>
 
 #ifdef CONFIG_MODULES
 
@@ -114,25 +115,74 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
        ret = -EOPNOTSUPP;
        rcu_read_lock();
        ops = rcu_dereference(lwtun_encaps[encap_type]);
+       if (likely(ops && ops->build_state))
+               ret = ops->build_state(dev, encap, family, cfg, lws);
+       rcu_read_unlock();
+
+       return ret;
+}
+EXPORT_SYMBOL(lwtunnel_build_state);
+
+int lwtunnel_valid_encap_type(u16 encap_type)
+{
+       const struct lwtunnel_encap_ops *ops;
+       int ret = -EINVAL;
+
+       if (encap_type == LWTUNNEL_ENCAP_NONE ||
+           encap_type > LWTUNNEL_ENCAP_MAX)
+               return ret;
+
+       rcu_read_lock();
+       ops = rcu_dereference(lwtun_encaps[encap_type]);
+       rcu_read_unlock();
 #ifdef CONFIG_MODULES
        if (!ops) {
                const char *encap_type_str = lwtunnel_encap_str(encap_type);
 
                if (encap_type_str) {
-                       rcu_read_unlock();
+                       __rtnl_unlock();
                        request_module("rtnl-lwt-%s", encap_type_str);
+                       rtnl_lock();
+
                        rcu_read_lock();
                        ops = rcu_dereference(lwtun_encaps[encap_type]);
+                       rcu_read_unlock();
                }
        }
 #endif
-       if (likely(ops && ops->build_state))
-               ret = ops->build_state(dev, encap, family, cfg, lws);
-       rcu_read_unlock();
+       return ops ? 0 : -EOPNOTSUPP;
+}
+EXPORT_SYMBOL(lwtunnel_valid_encap_type);
 
-       return ret;
+int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int remaining)
+{
+       struct rtnexthop *rtnh = (struct rtnexthop *)attr;
+       struct nlattr *nla_entype;
+       struct nlattr *attrs;
+       struct nlattr *nla;
+       u16 encap_type;
+       int attrlen;
+
+       while (rtnh_ok(rtnh, remaining)) {
+               attrlen = rtnh_attrlen(rtnh);
+               if (attrlen > 0) {
+                       attrs = rtnh_attrs(rtnh);
+                       nla = nla_find(attrs, attrlen, RTA_ENCAP);
+                       nla_entype = nla_find(attrs, attrlen, RTA_ENCAP_TYPE);
+
+                       if (nla_entype) {
+                               encap_type = nla_get_u16(nla_entype);
+
+                               if (lwtunnel_valid_encap_type(encap_type) != 0)
+                                       return -EOPNOTSUPP;
+                       }
+               }
+               rtnh = rtnh_next(rtnh, &remaining);
+       }
+
+       return 0;
 }
-EXPORT_SYMBOL(lwtunnel_build_state);
+EXPORT_SYMBOL(lwtunnel_valid_encap_type_attr);
 
 void lwtstate_free(struct lwtunnel_state *lws)
 {

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index eae0332b0e8c1f861ce629ed9ce3ddc45802a6b8..7db2ad2e82d3193ff1748bf393f536ba3a5a3eb9 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -46,6 +46,7 @@
 #include <net/rtnetlink.h>
 #include <net/xfrm.h>
 #include <net/l3mdev.h>
+#include <net/lwtunnel.h>
 #include <trace/events/fib.h>
 
 #ifndef CONFIG_IP_MULTIPLE_TABLES
@@ -677,6 +678,10 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
                        cfg->fc_mx_len = nla_len(attr);
                        break;
                case RTA_MULTIPATH:
+                       err = lwtunnel_valid_encap_type_attr(nla_data(attr),
+                                                            nla_len(attr));
+                       if (err < 0)
+                               goto errout;
                        cfg->fc_mp = nla_data(attr);
                        cfg->fc_mp_len = nla_len(attr);
                        break;
@@ -691,6 +696,9 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
                        break;
                case RTA_ENCAP_TYPE:
                        cfg->fc_encap_type = nla_get_u16(attr);
+                       err = lwtunnel_valid_encap_type(cfg->fc_encap_type);
+                       if (err < 0)
+                               goto errout;
                        break;
                }
        }

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4f6b067c8753a541bc20d6d9f6f4c5009c8956cb..7ea85370c11c81e8743e6a3086a32a0011f35d17 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2896,6 +2896,11 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
        if (tb[RTA_MULTIPATH]) {
                cfg->fc_mp = nla_data(tb[RTA_MULTIPATH]);
                cfg->fc_mp_len = nla_len(tb[RTA_MULTIPATH]);
+
+               err = lwtunnel_valid_encap_type_attr(cfg->fc_mp,
+                                                    cfg->fc_mp_len);
+               if (err < 0)
+                       goto errout;
        }
 
        if (tb[RTA_PREF]) {
@@ -2909,9 +2914,14 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
        if (tb[RTA_ENCAP])
                cfg->fc_encap = tb[RTA_ENCAP];
 
-       if (tb[RTA_ENCAP_TYPE])
+       if (tb[RTA_ENCAP_TYPE]) {
                cfg->fc_encap_type = nla_get_u16(tb[RTA_ENCAP_TYPE]);
 
+               err = lwtunnel_valid_encap_type(cfg->fc_encap_type);
+               if (err < 0)
+                       goto errout;
+       }
+
        if (tb[RTA_EXPIRES]) {
                unsigned long timeout = addrconf_timeout_fixup(nla_get_u32(tb[RTA_EXPIRES]), HZ);