AUDIT: Stop waiting for backlog after audit_panic() happens
We force a rate-limit on auditable events by making them wait for space
on the backlog queue. However, if auditd really is AWOL then this could
potentially bring the entire system to a halt, depending on the audit
rules in effect.
Firstly, make sure the wait time is honoured correctly -- it's the
maximum time the process should wait, rather than the time to wait
_each_ time round the loop. We were getting re-woken _each_ time a
packet was dequeued, and the timeout was being restarted each time.
Secondly, reset the wait time after audit_panic() is called. In general
this will be reset to zero, to allow progress to be made. If the system
is configured to _actually_ panic on audit_panic() then that will
already have happened; otherwise we know that audit records are being
lost anyway.
These two tunables can't be exposed via AUDIT_GET and AUDIT_SET because
those aren't particularly well-designed. It probably should have been
done by sysctls or sysfs anyway -- one for a later patch.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/kernel/audit.c b/kernel/audit.c
index 2617d05..b683f2b 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -79,6 +79,8 @@
/* Number of outstanding audit_buffers allowed. */
static int audit_backlog_limit = 64;
+static int audit_backlog_wait_time = 60 * HZ;
+static int audit_backlog_wait_overflow = 0;
/* The identity of the user shutting down the audit system. */
uid_t audit_sig_uid = -1;
@@ -655,6 +657,7 @@
struct timespec t;
unsigned int serial;
int reserve;
+ unsigned long timeout_start = jiffies;
if (!audit_initialized)
return NULL;
@@ -667,8 +670,9 @@
while (audit_backlog_limit
&& skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
- if (gfp_mask & __GFP_WAIT) {
- int ret = 1;
+ if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
+ && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {
+
/* Wait for auditd to drain the queue a little */
DECLARE_WAITQUEUE(wait, current);
set_current_state(TASK_INTERRUPTIBLE);
@@ -676,12 +680,11 @@
if (audit_backlog_limit &&
skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
- ret = schedule_timeout(HZ * 60);
+ schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
__set_current_state(TASK_RUNNING);
remove_wait_queue(&audit_backlog_wait, &wait);
- if (ret)
- continue;
+ continue;
}
if (audit_rate_check())
printk(KERN_WARNING
@@ -690,6 +693,8 @@
skb_queue_len(&audit_skb_queue),
audit_backlog_limit);
audit_log_lost("backlog limit exceeded");
+ audit_backlog_wait_time = audit_backlog_wait_overflow;
+ wake_up(&audit_backlog_wait);
return NULL;
}