[NETLINK]: Don't BUG on undersized allocations

Currently netlink users BUG when the allocated skb for an event
notification is undersized. While this is certainly a kernel bug,
its not critical and crashing the kernel is too drastic, especially
when considering that these errors have appeared multiple times in
the past and it BUGs even if no listeners are present.

This patch replaces BUG by WARN_ON and changes the notification
functions to inform potential listeners of undersized allocations
using a unique error code (EMSGSIZE).

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 39 insertions, 22 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 1df6cd4568d..215f1bff048 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -331,7 +331,7 @@ static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*frh), flags);
 	if (nlh == NULL)
-		return -1;
+		return -EMSGSIZE;
 
 	frh = nlmsg_data(nlh);
 	frh->table = rule->table;
@@ -359,7 +359,8 @@ static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 	return nlmsg_end(skb, nlh);
 
 nla_put_failure:
-	return nlmsg_cancel(skb, nlh);
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
 }
 
 int fib_rules_dump(struct sk_buff *skb, struct netlink_callback *cb, int family)
@@ -405,9 +406,12 @@ static void notify_rule_change(int event, struct fib_rule *rule,
 		goto errout;
 
 	err = fib_nl_fill_rule(skb, rule, pid, nlh->nlmsg_seq, event, 0, ops);
-	/* failure implies BUG in fib_rule_nlmsg_size() */
-	BUG_ON(err < 0);
-
+	if (err < 0) {
+		/* -EMSGSIZE implies BUG in fib_rule_nlmsg_size() */
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(skb);
+		goto errout;
+	}
 	err = rtnl_notify(skb, pid, ops->nlgroup, nlh, GFP_KERNEL);
 errout:
 	if (err < 0)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e7300b6b407..9e26f38ea6e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1637,7 +1637,7 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ndtmsg), flags);
 	if (nlh == NULL)
-		return -ENOBUFS;
+		return -EMSGSIZE;
 
 	ndtmsg = nlmsg_data(nlh);
 
@@ -1706,7 +1706,8 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
 
 nla_put_failure:
 	read_unlock_bh(&tbl->lock);
-	return nlmsg_cancel(skb, nlh);
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
 }
 
 static int neightbl_fill_param_info(struct sk_buff *skb,
@@ -1720,7 +1721,7 @@ static int neightbl_fill_param_info(struct sk_buff *skb,
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ndtmsg), flags);
 	if (nlh == NULL)
-		return -ENOBUFS;
+		return -EMSGSIZE;
 
 	ndtmsg = nlmsg_data(nlh);
 
@@ -1737,7 +1738,8 @@ static int neightbl_fill_param_info(struct sk_buff *skb,
 	return nlmsg_end(skb, nlh);
 errout:
 	read_unlock_bh(&tbl->lock);
-	return nlmsg_cancel(skb, nlh);
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
 }
  
 static inline struct neigh_parms *lookup_neigh_params(struct neigh_table *tbl,
@@ -1955,7 +1957,7 @@ static int neigh_fill_info(struct sk_buff *skb, struct neighbour *neigh,
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ndm), flags);
 	if (nlh == NULL)
-		return -ENOBUFS;
+		return -EMSGSIZE;
 
 	ndm = nlmsg_data(nlh);
 	ndm->ndm_family	 = neigh->ops->family;
@@ -1987,7 +1989,8 @@ static int neigh_fill_info(struct sk_buff *skb, struct neighbour *neigh,
 	return nlmsg_end(skb, nlh);
 
 nla_put_failure:
-	return nlmsg_cancel(skb, nlh);
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
 }
 
 
@@ -2429,9 +2432,12 @@ static void __neigh_notify(struct neighbour *n, int type, int flags)
 		goto errout;
 
 	err = neigh_fill_info(skb, n, 0, 0, type, flags);
-	/* failure implies BUG in neigh_nlmsg_size() */
-	BUG_ON(err < 0);
-
+	if (err < 0) {
+		/* -EMSGSIZE implies BUG in neigh_nlmsg_size() */
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(skb);
+		goto errout;
+	}
 	err = rtnl_notify(skb, 0, RTNLGRP_NEIGH, NULL, GFP_ATOMIC);
 errout:
 	if (err < 0)
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e76539a5eb5..9bf9ae05f15 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -320,7 +320,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
 	if (nlh == NULL)
-		return -ENOBUFS;
+		return -EMSGSIZE;
 
 	ifm = nlmsg_data(nlh);
 	ifm->ifi_family = AF_UNSPEC;
@@ -384,7 +384,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 	return nlmsg_end(skb, nlh);
 
 nla_put_failure:
-	return nlmsg_cancel(skb, nlh);
+	nlmsg_cancel(skb, nlh);
+	return -EMSGSIZE;
 }
 
 static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
@@ -633,9 +634,12 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 
 	err = rtnl_fill_ifinfo(nskb, dev, iw, iw_buf_len, RTM_NEWLINK,
 			       NETLINK_CB(skb).pid, nlh->nlmsg_seq, 0, 0);
-	/* failure impilies BUG in if_nlmsg_size or wireless_rtnetlink_get */
-	BUG_ON(err < 0);
-
+	if (err < 0) {
+		/* -EMSGSIZE implies BUG in if_nlmsg_size */
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(nskb);
+		goto errout;
+	}
 	err = rtnl_unicast(nskb, NETLINK_CB(skb).pid);
 errout:
 	kfree(iw_buf);
@@ -678,9 +682,12 @@ void rtmsg_ifinfo(int type, struct net_device *dev, unsigned change)
 		goto errout;
 
 	err = rtnl_fill_ifinfo(skb, dev, NULL, 0, type, 0, 0, change, 0);
-	/* failure implies BUG in if_nlmsg_size() */
-	BUG_ON(err < 0);
-
+	if (err < 0) {
+		/* -EMSGSIZE implies BUG in if_nlmsg_size() */
+		WARN_ON(err == -EMSGSIZE);
+		kfree_skb(skb);
+		goto errout;
+	}
 	err = rtnl_notify(skb, 0, RTNLGRP_LINK, NULL, GFP_KERNEL);
 errout:
 	if (err < 0)