Generate audit NETFILTER_CFG records on ebtables table registration.

Previously this was only being done for all x_tables operations and ebtables
table replacement.

Audit only when there is an existing syscall audit rule, otherwise issue a
standalone record only on table modification rather than empty table creation.
Include subject attributes to the new standalone NETFILTER_CFGSOLO record using
audit_log_task().

Here is a sample accompanied record:
  type=NETFILTER_CFG msg=audit(1494907217.558:5403): family=7 table=filter 
entries=0

and unaccompanied case:
  type=UNKNOWN[1331] msg=audit(1494723394.832:111): auid=4294967295 uid=0 gid=0 
ses=4294967295 subj=system_u:system_r:iptables_t:s0 pid=556 
comm="ebtables-restor" exe="/usr/sbin/ebtables-restore" family=7 table=broute 
entries=1

See: https://github.com/linux-audit/audit-kernel/issues/43

Signed-off-by: Richard Guy Briggs <[email protected]>
---
 net/bridge/netfilter/ebtables.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 743f9e6..7499232 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1251,6 +1251,32 @@ struct ebt_table * ebt_register_table(struct net *net,
        }
        list_add(&table->list, &net->xt.tables[NFPROTO_BRIDGE]);
        mutex_unlock(&ebt_mutex);
+#ifdef CONFIG_AUDIT
+       if (audit_enabled) {
+               struct audit_buffer *ab;
+
+               if(!audit_dummy_context()) {
+                       ab = audit_log_start(current->audit_context, GFP_KERNEL,
+                                            AUDIT_NETFILTER_CFG);
+                       if (ab) {
+                               audit_log_format(ab, "family=%u table=%s 
entries=%u",
+                                                AF_BRIDGE, repl->name,
+                                                repl->nentries);
+                               audit_log_end(ab);
+                       }
+               } else if(repl->nentries) {
+                       ab = audit_log_start(NULL, GFP_KERNEL,
+                                            AUDIT_NETFILTER_CFGSOLO);
+                       if (ab) {
+                               audit_log_task(ab);
+                               audit_log_format(ab, " family=%u table=%s 
entries=%u",
+                                                AF_BRIDGE, repl->name,
+                                                repl->nentries);
+                               audit_log_end(ab);
+                       }
+               }
+       }
+#endif
        return table;
 free_unlock:
        mutex_unlock(&ebt_mutex);
-- 
1.7.1

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