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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: 745041e2aa ("lwtunnel: autoload of lwt modules")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2017-01-17 14:57:36 -08:00 committed by David S. Miller
parent 719ca81114
commit 9ed59592e3
4 changed files with 92 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/net/lwtunnel.h
View File

@ -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,

74
net/core/lwtunnel.c
View File

@ -26,6 +26,7 @@
#include <net/lwtunnel.h>
#include <net/rtnetlink.h>
#include <net/ip6_fib.h>
#include <net/nexthop.h>
#ifdef CONFIG_MODULES
@ -114,18 +115,6 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[encap_type]);
#ifdef CONFIG_MODULES
if (!ops) {
const char *encap_type_str = lwtunnel_encap_str(encap_type);
if (encap_type_str) {
rcu_read_unlock();
request_module("rtnl-lwt-%s", encap_type_str);
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[encap_type]);
}
}
#endif
if (likely(ops && ops->build_state))
ret = ops->build_state(dev, encap, family, cfg, lws);
rcu_read_unlock();
@ -134,6 +123,67 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type,
}
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) {
__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
return ops ? 0 : -EOPNOTSUPP;
}
EXPORT_SYMBOL(lwtunnel_valid_encap_type);
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_valid_encap_type_attr);
void lwtstate_free(struct lwtunnel_state *lws)
{
const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type];

8
net/ipv4/fib_frontend.c
View File

@ -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;
}
}

12
net/ipv6/route.c
View File

@ -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);