[PATCH 1/2] fix audit skb leak on congested netlink socket

[Chris Wright]

When auditd is congested the kernel's audit system leaks skb's.  First,
it takes them off the audit_buffer sklist at which point they are lost,
second, it allocates a new skb with 0 length payload.  Then (likely still
congested), it repeats this losing the new skb.  Plug the leak by making
sure to requeue the skb, and avoid audit_log_move() on 0 len audit_buffer.

Signed-off-by: Chris Wright <chrisw@xxxxxxxx>

===== kernel/audit.c 1.6 vs edited =====
--- 1.6/kernel/audit.c	2005-01-20 20:56:04 -08:00
+++ edited/kernel/audit.c	2005-01-25 14:34:32 -08:00
@@ -494,6 +494,10 @@ static void audit_log_move(struct audit_
 	char		*start;
 	int		extra = ab->nlh ? 0 : NLMSG_SPACE(0);
 
+	/* possible resubmission */
+	if (ab->len == 0)
+		return;
+
 	skb = skb_peek(&ab->sklist);
 	if (!skb || skb_tailroom(skb) <= ab->len + extra) {
 		skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC);
@@ -535,6 +539,7 @@ static inline int audit_log_drain(struct
 		}
 		if (retval == -EAGAIN && ab->count < 5) {
 			++ab->count;
+			skb_queue_tail(&ab->sklist, skb);
 			audit_log_end_irq(ab);
 			return 1;
 		}
-
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