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Commit 9ed59592 authored by David Ahern's avatar David Ahern Committed by David S. Miller
Browse files

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: 745041e2 ("lwtunnel: autoload of lwt modules")
Signed-off-by: default avatarDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 719ca811

include/net/lwtunnel.h

+11 −0
Original line number Diff line number Diff line
@@ -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,

net/core/lwtunnel.c

+56 −6
Original line number Diff line number Diff line
@@ -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;

			}

EXPORT_SYMBOL(lwtunnel_build_state);

		}

		rtnh = rtnh_next(rtnh, &remaining);

	}



	return 0;

}

EXPORT_SYMBOL(lwtunnel_valid_encap_type_attr);



void lwtstate_free(struct lwtunnel_state *lws)

{

net/ipv4/fib_frontend.c

+8 −0
Original line number Diff line number Diff line
@@ -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;

		}

	}

net/ipv6/route.c

+11 −1
Original line number Diff line number Diff line
@@ -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);