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Subject[PATCH] audit: fix wrong timeout value in audit_log_start
Date
audit_log_start() does not properly check timeout values when
audit_backlog_limit is exceeded, for example it is possible to use
negative timeout values with schedule_timeout() triggering error
messages like this:

schedule_timeout: wrong timeout value ffffffffffff54e4

Be sure to never set negative values for the timeout.

Also, do a small refactoring to improve code readability.

Reported-by: Sean Jenkins <sean@bluehost.com>
Signed-off-by: Andrea Righi <andrea@betterlinux.com>
---
kernel/audit.c | 46 ++++++++++++++++++++++++++++++----------------
1 file changed, 30 insertions(+), 16 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index ea3b7b6..362d9b4 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1123,6 +1123,28 @@ static inline void audit_get_stamp(struct audit_context *ctx,
}
}

+/* Wait for auditd to drain the queue a little */
+static void audit_log_congestion_wait(unsigned long timeout_start)
+{
+ DECLARE_WAITQUEUE(wait, current);
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ add_wait_queue(&audit_backlog_wait, &wait);
+
+ if (audit_backlog_limit &&
+ skb_queue_len(&audit_skb_queue) > audit_backlog_limit) {
+ unsigned long deadline, now = ACCESS_ONCE(jiffies);
+
+ WARN_ON(time_after(timeout_start, now));
+ deadline = timeout_start + audit_backlog_wait_time;
+ if (time_before(now, deadline))
+ schedule_timeout(deadline - now);
+ }
+
+ __set_current_state(TASK_RUNNING);
+ remove_wait_queue(&audit_backlog_wait, &wait);
+}
+
/* Obtain an audit buffer. This routine does locking to obtain the
* audit buffer, but then no locking is required for calls to
* audit_log_*format. If the tsk is a task that is currently in a
@@ -1166,22 +1188,14 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
reserve = 5; /* Allow atomic callers to go up to five
entries over the normal backlog limit */

- while (audit_backlog_limit
- && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
- 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);
- add_wait_queue(&audit_backlog_wait, &wait);
-
- if (audit_backlog_limit &&
- skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
- schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
-
- __set_current_state(TASK_RUNNING);
- remove_wait_queue(&audit_backlog_wait, &wait);
+ while (audit_backlog_limit &&
+ skb_queue_len(&audit_skb_queue) >
+ audit_backlog_limit + reserve) {
+ if ((gfp_mask & __GFP_WAIT) &&
+ audit_backlog_wait_time &&
+ time_is_after_jiffies(timeout_start +
+ audit_backlog_wait_time)) {
+ audit_log_congestion_wait(timeout_start);
continue;
}
if (audit_rate_check() && printk_ratelimit())
--
1.7.9.5


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