audit: Use struct net not pid_t to remember the network namespce to reply in

While reading through 3.14-rc1 I found a pretty siginficant mishandling
of network namespaces in the recent audit changes.

In struct audit_netlink_list and audit_reply add a reference to the
network namespace of the caller and remove the userspace pid of the
caller.  This cleanly remembers the callers network namespace, and
removes a huge class of races and nasty failure modes that can occur
when attempting to relook up the callers network namespace from a pid_t
(including the caller's network namespace changing, pid wraparound, and
the pid simply not being present).

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 34c5a2310fbf..71fb41f393d7 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -182,7 +182,7 @@ struct audit_buffer {
 
 struct audit_reply {
         __u32 portid;
-        pid_t pid;
+        struct net *net;
         struct sk_buff *skb;
 };
 
@@ -500,7 +500,7 @@ int audit_send_list(void *_dest)
 {
         struct audit_netlink_list *dest = _dest;
         struct sk_buff *skb;
-        struct net *net = get_net_ns_by_pid(dest->pid);
+        struct net *net = dest->net;
         struct audit_net *aunet = net_generic(net, audit_net_id);
 
         /* wait for parent to finish and send an ACK */
@@ -510,6 +510,7 @@ int audit_send_list(void *_dest)
         while ((skb = __skb_dequeue(&dest->q)) != NULL)
                 netlink_unicast(aunet->nlsk, skb, dest->portid, 0);
 
+        put_net(net);
         kfree(dest);
 
         return 0;
@@ -543,7 +544,7 @@ out_kfree_skb:
 static int audit_send_reply_thread(void *arg)
 {
         struct audit_reply *reply = (struct audit_reply *)arg;
-        struct net *net = get_net_ns_by_pid(reply->pid);
+        struct net *net = reply->net;
         struct audit_net *aunet = net_generic(net, audit_net_id);
 
         mutex_lock(&audit_cmd_mutex);
@@ -552,6 +553,7 @@ static int audit_send_reply_thread(void *arg)
         /* Ignore failure. It'll only happen if the sender goes away,
            because our timeout is set to infinite. */
         netlink_unicast(aunet->nlsk , reply->skb, reply->portid, 0);
+        put_net(net);
         kfree(reply);
         return 0;
 }
@@ -583,8 +585,8 @@ static void audit_send_reply(__u32 portid, int seq, int type, int done,
         if (!skb)
                 goto out;
 
+        reply->net = get_net(current->nsproxy->net_ns);
         reply->portid = portid;
-        reply->pid = task_pid_vnr(current);
         reply->skb = skb;
 
         tsk = kthread_run(audit_send_reply_thread, reply, "audit_send_reply");