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audit: don't ever sleep on a command record/message

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Sleeping on a command record/message in audit_log_start() could slow
something, e.g. auditd, from doing something important, e.g. clean
shutdown, which could present problems on a heavily loaded system.
This patch allows tasks to bypass any queue restrictions if they are
logging a command record/message.

Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Paul Moore 2016-11-29 16:53:26 -05:00
parent 6c54e78996
commit a09cfa4708
1 changed files with 13 additions and 5 deletions
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18
kernel/audit.c
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@ -1488,11 +1488,19 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
if (unlikely(!audit_filter(type, AUDIT_FILTER_TYPE)))
return NULL;
/* don't ever fail/sleep on auditd since we need auditd to drain the
* queue; also, when we are checking for auditd, compare PIDs using
* task_tgid_vnr() since auditd_pid is set in audit_receive_msg() using
* a PID anchored in the caller's namespace */
if (!(audit_pid && audit_pid == task_tgid_vnr(current))) {
/* don't ever fail/sleep on these two conditions:
* 1. auditd generated record - since we need auditd to drain the
* queue; also, when we are checking for auditd, compare PIDs using
* task_tgid_vnr() since auditd_pid is set in audit_receive_msg()
* using a PID anchored in the caller's namespace
* 2. audit command message - record types 1000 through 1099 inclusive
* are command messages/records used to manage the kernel subsystem
* and the audit userspace, blocking on these messages could cause
* problems under load so don't do it (note: not all of these
* command types are valid as record types, but it is quicker to
* just check two ints than a series of ints in a if/switch stmt) */
if (!((audit_pid && audit_pid == task_tgid_vnr(current)) ||
(type >= 1000 && type <= 1099))) {
long sleep_time = audit_backlog_wait_time;
while (audit_backlog_limit &&