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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>
This commit is contained in:
David Woodhouse 2005-07-02 14:08:48 +01:00
parent 7b430437c0
commit ac4cec443a
1 changed files with 10 additions and 5 deletions
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15
kernel/audit.c
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@ -79,6 +79,8 @@ static int audit_rate_limit;
/* 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 audit_buffer *audit_log_start(struct audit_context *ctx, int gfp_mask,
struct timespec t;
unsigned int serial;
int reserve;
unsigned long timeout_start = jiffies;
if (!audit_initialized)
return NULL;
@ -667,8 +670,9 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, int gfp_mask,
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 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, int gfp_mask,
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 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, int gfp_mask,
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;
}