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

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) -- 1.7.1