audit: printk before dropping logs in audit_log_end

[PATCH next] audit: printk before dropping logs in audit_log_end

Posted by Ecronic 3 years, 7 months ago

If the log rate of audit exceeds audit_rate_limit, audit_log_end
will drop the audit logs. Printk before dropping them may be a
better choice.

Signed-off-by: Ecronic <ecronic@outlook.com>
---
 kernel/audit.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index a75978ae38ad..3f5be93447cb 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2415,10 +2415,10 @@ void audit_log_end(struct audit_buffer *ab)
 	if (!ab)
 		return;
 
-	if (audit_rate_check()) {
-		skb = ab->skb;
-		ab->skb = NULL;
+	skb = ab->skb;
+	ab->skb = NULL;
 
+	if (audit_rate_check()) {
 		/* setup the netlink header, see the comments in
 		 * kauditd_send_multicast_skb() for length quirks */
 		nlh = nlmsg_hdr(skb);
@@ -2427,8 +2427,11 @@ void audit_log_end(struct audit_buffer *ab)
 		/* queue the netlink packet and poke the kauditd thread */
 		skb_queue_tail(&audit_queue, skb);
 		wake_up_interruptible(&kauditd_wait);
-	} else
+	} else {
+		kauditd_printk_skb(skb);
+		kfree_skb(skb);
 		audit_log_lost("rate limit exceeded");
+	}
 
 	audit_buffer_free(ab);
 }
-- 
2.30.0

Re: [PATCH next] audit: printk before dropping logs in audit_log_end

Posted by Paul Moore 3 years, 7 months ago

On Sun, Aug 21, 2022 at 10:22 AM Ecronic <ecronic@outlook.com> wrote:
>
> If the log rate of audit exceeds audit_rate_limit, audit_log_end
> will drop the audit logs. Printk before dropping them may be a
> better choice.
>
> Signed-off-by: Ecronic <ecronic@outlook.com>
> ---
>  kernel/audit.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Hi Ecronic,

I'm not sure this is the right approach; if we're hitting a rate
limit, printing the record to the console is likely the last thing we
want to do.  Are you currently hitting a problem with the rate
limiting, or is this simply something you found via code inspection?

> diff --git a/kernel/audit.c b/kernel/audit.c
> index a75978ae38ad..3f5be93447cb 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2415,10 +2415,10 @@ void audit_log_end(struct audit_buffer *ab)
>         if (!ab)
>                 return;
>
> -       if (audit_rate_check()) {
> -               skb = ab->skb;
> -               ab->skb = NULL;
> +       skb = ab->skb;
> +       ab->skb = NULL;
>
> +       if (audit_rate_check()) {
>                 /* setup the netlink header, see the comments in
>                  * kauditd_send_multicast_skb() for length quirks */
>                 nlh = nlmsg_hdr(skb);
> @@ -2427,8 +2427,11 @@ void audit_log_end(struct audit_buffer *ab)
>                 /* queue the netlink packet and poke the kauditd thread */
>                 skb_queue_tail(&audit_queue, skb);
>                 wake_up_interruptible(&kauditd_wait);
> -       } else
> +       } else {
> +               kauditd_printk_skb(skb);
> +               kfree_skb(skb);
>                 audit_log_lost("rate limit exceeded");
> +       }
>
>         audit_buffer_free(ab);
>  }
> --
> 2.30.0

-- 
paul-moore.com