net: hold rtnl again in dump callbacks

Commit e67f88dd12f6 (dont hold rtnl mutex during netlink dump callbacks)
missed fact that rtnl_fill_ifinfo() must be called with rtnl held.

Because of possible deadlocks between two mutexes (cb_mutex and rtnl),
its not easy to solve this problem, so revert this part of the patch.

It also forgot one rcu_read_unlock() in FIB dump_rules()

Add one ASSERT_RTNL() in rtnl_fill_ifinfo() to remind us the rule.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 2 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 3911586e12e4..008dc70b064b 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -602,6 +602,7 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
 skip:
                 idx++;
         }
+        rcu_read_unlock();
         cb->args[1] = idx;
         rules_ops_put(ops);
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d1644e317e70..2d56cb9b0b94 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -850,6 +850,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
         struct nlattr *attr, *af_spec;
         struct rtnl_af_ops *af_ops;
 
+        ASSERT_RTNL();
         nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
         if (nlh == NULL)
                 return -EMSGSIZE;
@@ -1876,6 +1877,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
         int min_len;
         int family;
         int type;
+        int err;
 
         type = nlh->nlmsg_type;
         if (type > RTM_MAX)
@@ -1902,8 +1904,11 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                 if (dumpit == NULL)
                         return -EOPNOTSUPP;
 
+                __rtnl_unlock();
                 rtnl = net->rtnl;
-                return netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
+                err = netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
+                rtnl_lock();
+                return err;
         }
 
         memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
@@ -1975,7 +1980,7 @@ static int __net_init rtnetlink_net_init(struct net *net)
 {
         struct sock *sk;
         sk = netlink_kernel_create(net, NETLINK_ROUTE, RTNLGRP_MAX,
-                                   rtnetlink_rcv, NULL, THIS_MODULE);
+                                   rtnetlink_rcv, &rtnl_mutex, THIS_MODULE);
         if (!sk)
                 return -ENOMEM;
         net->rtnl = sk;