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

[Richard Guy Briggs]

On 15/09/07, 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@xxxxxxxxxx>

Ok, self-nack on this one for a couple of problems...
netlink_getsockbyportid() is static to af_netlink.c and "pid" should be
task_tgid_vnr(current).  Otherwise, any opinions on this approach?

> ---
> 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
> 

- RGB

--
Richard Guy Briggs <rbriggs@xxxxxxxxxx>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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