[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>

1 files changed, 9 insertions, 5 deletions

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index a9139682c49b..7d68b24b5654 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -45,7 +45,7 @@ static int br_fill_ifinfo(struct sk_buff *skb, const struct net_bridge_port *por
 
         nlh = nlmsg_put(skb, pid, seq, event, sizeof(*hdr), flags);
         if (nlh == NULL)
-                return -ENOBUFS;
+                return -EMSGSIZE;
 
         hdr = nlmsg_data(nlh);
         hdr->ifi_family = AF_BRIDGE;
@@ -72,7 +72,8 @@ static int br_fill_ifinfo(struct sk_buff *skb, const struct net_bridge_port *por
         return nlmsg_end(skb, nlh);
 
 nla_put_failure:
-        return nlmsg_cancel(skb, nlh);
+        nlmsg_cancel(skb, nlh);
+        return -EMSGSIZE;
 }
 
 /*
@@ -89,9 +90,12 @@ void br_ifinfo_notify(int event, struct net_bridge_port *port)
                 goto errout;
 
         err = br_fill_ifinfo(skb, port, 0, 0, event, 0);
-        /* failure implies BUG in br_nlmsg_size() */
-        BUG_ON(err < 0);
-
+        if (err < 0) {
+                /* -EMSGSIZE implies BUG in br_nlmsg_size() */
+                WARN_ON(err == -EMSGSIZE);
+                kfree_skb(skb);
+                goto errout;
+        }
         err = rtnl_notify(skb, 0, RTNLGRP_LINK, NULL, GFP_ATOMIC);
 errout:
         if (err < 0)