Re: [PATCH V1] audit: add warning that an old auditd may be starved out by a new auditd

This is already going to be in the audit log, right? We're going to send a CONFIG_CHANGE record with old_pid == the existing auditd. I bet it gets delivered to the old auditd.

But why is this a printk(KERN_WARN) ?

On Mon, 2015-09-07 at 12:48 -0400, Richard Guy Briggs wrote: > Nothing prevents a new auditd starting up and replacing a valid > audit_pid when an old auditd is still running, effectively starving out > the old auditd since audit_pid no longer points to the old valid auditd. > > There isn't an easy way to detect if an old auditd is still running on > the existing audit_pid other than attempting to send a message to see if > it fails. If no message to auditd has been attempted since auditd died > unnaturally or got killed, audit_pid will still indicate it is alive. > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > --- > Note: Would it be too bold to actually block the registration of a new > auditd if the netlink_getsockbyportid() call succeeded? Would other > checks be appropriate? > > kernel/audit.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/kernel/audit.c b/kernel/audit.c > index 18cdfe2..1fa1e0d 100644 > --- a/kernel/audit.c > +++ b/kernel/audit.c > @@ -872,6 +872,11 @@ static int audit_receive_msg(struct sk_buff > *skb, struct nlmsghdr *nlh) > if (s.mask & AUDIT_STATUS_PID) { > int new_pid = s.pid; > > + if (audit_pid && new_pid && > + !IS_ERR(netlink_getsockbyportid(audit_sock, audit_nlk_portid))) > + pr_warn("auditd replaced by new auditd before normal shutdown: " > + "(old)audit_pid=%d (by)pid=%d new_pid=%d", > + audit_pid, pid, new_pid); > if ((!new_pid) && (task_tgid_vnr(current) != audit_pid)) > return -EACCES; > if (audit_enabled != AUDIT_OFF)