On Thu, Dec 8, 2016 at 10:02 PM, Richard Guy Briggs <r...@redhat.com> wrote:
> I also tried to extend Cong Wang's idea to attempt to proactively respond to a
> NETLINK_URELEASE on the audit_sock and reset it, but ran into a locking error
> stack dump using mutex_lock(&audit_cmd_mutex) in the notifier callback.
> Eliminating the lock since the sock is dead anways eliminates the error.
>
> Is it safe? I'll resubmit if this looks remotely sane. Meanwhile I'll try to
> get the test case to compile.
It doesn't look safe, because 'audit_sock', 'audit_nlk_portid' and 'audit_pid'
are updated as a whole and race between audit_receive_msg() and
NETLINK_URELEASE.
> @@ -1167,10 +1190,14 @@ static void __net_exit audit_net_exit(struct net *net)
> {
> struct audit_net *aunet = net_generic(net, audit_net_id);
> struct sock *sock = aunet->nlsk;
> +
> + mutex_lock(&audit_cmd_mutex);
> if (sock == audit_sock) {
> audit_pid = 0;
> + audit_nlk_portid = 0;
> audit_sock = NULL;
> }
> + mutex_unlock(&audit_cmd_mutex);
>
If you decide to use NETLINK_URELEASE notifier, the above piece is no
longer needed, the net_exit path simply releases a refcnt.
