[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/ipv4/devinet.c b/net/ipv4/devinet.c
index 480ace9819f6..c40203640966 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1140,7 +1140,7 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
 
         nlh = nlmsg_put(skb, pid, seq, event, sizeof(*ifm), flags);
         if (nlh == NULL)
-                return -ENOBUFS;
+                return -EMSGSIZE;
 
         ifm = nlmsg_data(nlh);
         ifm->ifa_family = AF_INET;
@@ -1167,7 +1167,8 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
         return nlmsg_end(skb, nlh);
 
 nla_put_failure:
-        return nlmsg_cancel(skb, nlh);
+        nlmsg_cancel(skb, nlh);
+        return -EMSGSIZE;
 }
 
 static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
@@ -1225,9 +1226,12 @@ static void rtmsg_ifa(int event, struct in_ifaddr* ifa, struct nlmsghdr *nlh,
                 goto errout;
 
         err = inet_fill_ifaddr(skb, ifa, pid, seq, event, 0);
-        /* failure implies BUG in inet_nlmsg_size() */
-        BUG_ON(err < 0);
-
+        if (err < 0) {
+                /* -EMSGSIZE implies BUG in inet_nlmsg_size() */
+                WARN_ON(err == -EMSGSIZE);
+                kfree_skb(skb);
+                goto errout;
+        }
         err = rtnl_notify(skb, pid, RTNLGRP_IPV4_IFADDR, nlh, GFP_KERNEL);
 errout:
         if (err < 0)