net: Improve handling of failures on link and route dumps

BugLink: http://bugs.launchpad.net/bugs/1697001
[ Upstream commit f6c5775ff0bfa62b072face6bf1d40f659f194b2 ]

In general, rtnetlink dumps do not anticipate failure to dump a single
object (e.g., link or route) on a single pass. As both route and link
objects have grown via more attributes, that is no longer a given.

netlink dumps can handle a failure if the dump function returns an
error; specifically, netlink_dump adds the return code to the response
if it is <= 0 so userspace is notified of the failure. The missing
piece is the rtnetlink dump functions returning the error.

Fix route and link dump functions to return the errors if no object is
added to an skb (detected by skb->len != 0). IPv6 route dumps
(rt6_dump_route) already return the error; this patch updates IPv4 and
link dumps. Other dump functions may need to be ajusted as well.

Reported-by: Jan Moskyto Matejka <mq@ucw.cz>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index fe38ef58997c203ba0954f58f1574c7d6de7b35b..d43544ce7550814017dee25f631b3be18bcccb8a 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1458,13 +1458,13 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
                                               cb->nlh->nlmsg_seq, 0,
                                               NLM_F_MULTI,
                                               ext_filter_mask);
-                       /* If we ran out of room on the first message,
-                        * we're in trouble
-                        */
-                       WARN_ON((err == -EMSGSIZE) && (skb->len == 0));
 
-                       if (err < 0)
-                               goto out;
+                       if (err < 0) {
+                               if (likely(skb->len))
+                                       goto out;
+
+                               goto out_err;
+                       }
 
                        nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 cont:
@@ -1472,10 +1472,12 @@ cont:
                }
        }
 out:
+       err = skb->len;
+out_err:
        cb->args[1] = idx;
        cb->args[0] = h;
 
-       return skb->len;
+       return err;
 }
 
 int rtnl_nla_parse_ifla(struct nlattr **tb, const struct nlattr *head, int len)
@@ -3127,8 +3129,12 @@ static int rtnl_bridge_getlink(struct sk_buff *skb, struct netlink_callback *cb)
                                err = br_dev->netdev_ops->ndo_bridge_getlink(
                                                skb, portid, seq, dev,
                                                filter_mask, NLM_F_MULTI);
-                               if (err < 0 && err != -EOPNOTSUPP)
-                                       break;
+                               if (err < 0 && err != -EOPNOTSUPP) {
+                                       if (likely(skb->len))
+                                               break;
+
+                                       goto out_err;
+                               }
                        }
                        idx++;
                }
@@ -3139,16 +3145,22 @@ static int rtnl_bridge_getlink(struct sk_buff *skb, struct netlink_callback *cb)
                                                              seq, dev,
                                                              filter_mask,
                                                              NLM_F_MULTI);
-                               if (err < 0 && err != -EOPNOTSUPP)
-                                       break;
+                               if (err < 0 && err != -EOPNOTSUPP) {
+                                       if (likely(skb->len))
+                                               break;
+
+                                       goto out_err;
+                               }
                        }
                        idx++;
                }
        }
+       err = skb->len;
+out_err:
        rcu_read_unlock();
        cb->args[0] = idx;
 
-       return skb->len;
+       return err;
 }
 
 static inline size_t bridge_nlmsg_size(void)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 1adba44f8fbcfc9ff4dac92d3853d5e87af243fe..66dcb529fd9c711050296d155be14bf754d6f06d 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -757,7 +757,7 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
        unsigned int e = 0, s_e;
        struct fib_table *tb;
        struct hlist_head *head;
-       int dumped = 0;
+       int dumped = 0, err;
 
        if (nlmsg_len(cb->nlh) >= sizeof(struct rtmsg) &&
            ((struct rtmsg *) nlmsg_data(cb->nlh))->rtm_flags & RTM_F_CLONED)
@@ -777,20 +777,27 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
                        if (dumped)
                                memset(&cb->args[2], 0, sizeof(cb->args) -
                                                 2 * sizeof(cb->args[0]));
-                       if (fib_table_dump(tb, skb, cb) < 0)
-                               goto out;
+                       err = fib_table_dump(tb, skb, cb);
+                       if (err < 0) {
+                               if (likely(skb->len))
+                                       goto out;
+
+                               goto out_err;
+                       }
                        dumped = 1;
 next:
                        e++;
                }
        }
 out:
+       err = skb->len;
+out_err:
        rcu_read_unlock();
 
        cb->args[1] = e;
        cb->args[0] = h;
 
-       return skb->len;
+       return err;
 }
 
 /* Prepare and feed intra-kernel routing request.

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 7c52afb98c424e162418d404512dbe37705dac3d..5c598f99a500a9b71110e972adf68e41c5c7fefe 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1906,6 +1906,8 @@ static int fn_trie_dump_leaf(struct key_vector *l, struct fib_table *tb,
 
        /* rcu_read_lock is hold by caller */
        hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
+               int err;
+
                if (i < s_i) {
                        i++;
                        continue;
@@ -1916,17 +1918,14 @@ static int fn_trie_dump_leaf(struct key_vector *l, struct fib_table *tb,
                        continue;
                }
 
-               if (fib_dump_info(skb, NETLINK_CB(cb->skb).portid,
-                                 cb->nlh->nlmsg_seq,
-                                 RTM_NEWROUTE,
-                                 tb->tb_id,
-                                 fa->fa_type,
-                                 xkey,
-                                 KEYLENGTH - fa->fa_slen,
-                                 fa->fa_tos,
-                                 fa->fa_info, NLM_F_MULTI) < 0) {
+               err = fib_dump_info(skb, NETLINK_CB(cb->skb).portid,
+                                   cb->nlh->nlmsg_seq, RTM_NEWROUTE,
+                                   tb->tb_id, fa->fa_type,
+                                   xkey, KEYLENGTH - fa->fa_slen,
+                                   fa->fa_tos, fa->fa_info, NLM_F_MULTI);
+               if (err < 0) {
                        cb->args[4] = i;
-                       return -1;
+                       return err;
                }
                i++;
        }
@@ -1948,10 +1947,13 @@ int fib_table_dump(struct fib_table *tb, struct sk_buff *skb,
        t_key key = cb->args[3];
 
        while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
-               if (fn_trie_dump_leaf(l, tb, skb, cb) < 0) {
+               int err;
+
+               err = fn_trie_dump_leaf(l, tb, skb, cb);
+               if (err < 0) {
                        cb->args[3] = key;
                        cb->args[2] = count;
-                       return -1;
+                       return err;
                }
 
                ++count;