[RFC PATCH 5/7] audit: allow audit_cmd_mutex holders to use reserves
If we hold the audit_cmd_mutex, we should never sleep waiting for auditd
to drain the queue since auditd may need the mutex to shut down.
This was first implemented with mutex_trylock(), but since
audit_log_start() can be called in softirq context, that won't work.
Next, owner_running() was used to check audit_cmd_mutex but another
process could have this locked on another cpu. Use rcu_read_lock() and
ACCESS_ONCE() to check audit_cmd_mutex.
Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com>
---
kernel/audit.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/audit.c b/kernel/audit.c
index 02a5ec0..34411af 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1376,12 +1376,15 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx,
gfp_t gfp_mask,
return NULL;
if (gfp_mask & __GFP_WAIT) {
- if (current->tgid == 1 || (audit_pid && audit_pid == current->tgid))
+ rcu_read_lock();
+ if (ACCESS_ONCE(audit_cmd_mutex.owner) == current ||
+ current->tgid == 1 ||
+ (audit_pid && audit_pid == current->tgid))
gfp_mask &= ~__GFP_WAIT;
else
reserve = 0;
+ rcu_read_unlock();
}
-
while (audit_backlog_limit
&& skb_queue_len(&audit_skb_queue) > audit_backlog_limit +
reserve) {
if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time) {
--
1.7.1