Patch "net: Improve handling of failures on link and route dumps" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    net: Improve handling of failures on link and route dumps

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-improve-handling-of-failures-on-link-and-route-dumps.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed May 31 09:13:34 JST 2017
From: David Ahern <dsahern@gmail.com>
Date: Mon, 15 May 2017 23:19:17 -0700
Subject: net: Improve handling of failures on link and route dumps

From: David Ahern <dsahern@gmail.com>


[ 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>
---
 net/core/rtnetlink.c    |   36 ++++++++++++++++++++++++------------
 net/ipv4/fib_frontend.c |   15 +++++++++++----
 net/ipv4/fib_trie.c     |   26 ++++++++++++++------------
 3 files changed, 49 insertions(+), 28 deletions(-)

--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1617,13 +1617,13 @@ static int rtnl_dump_ifinfo(struct sk_bu
 					       cb->nlh->nlmsg_seq, 0,
 					       flags,
 					       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:
@@ -1631,10 +1631,12 @@ 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)
@@ -3413,8 +3415,12 @@ static int rtnl_bridge_getlink(struct sk
 				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++;
 		}
@@ -3425,16 +3431,22 @@ static int rtnl_bridge_getlink(struct sk
 							      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)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -758,7 +758,7 @@ static int inet_dump_fib(struct sk_buff
 	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)
@@ -778,20 +778,27 @@ static int inet_dump_fib(struct sk_buff
 			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.
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1932,6 +1932,8 @@ static int fn_trie_dump_leaf(struct key_
 
 	/* 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;
@@ -1942,17 +1944,14 @@ static int fn_trie_dump_leaf(struct key_
 			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++;
 	}
@@ -1974,10 +1973,13 @@ int fib_table_dump(struct fib_table *tb,
 	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;


Patches currently in stable-queue which might be from dsahern@gmail.com are

queue-4.9/net-improve-handling-of-failures-on-link-and-route-dumps.patch