Many applications explicitly set SCHED_NORMAL on threads thus undoing the
usefulness of the SCHED_ISO, SCHED_BATCH and SCHED_IDLEPRIO policies.
For unprivileged users:
Only allow non realtime policies to be downgraded from ISO->BATCH->IDLEPRIO
but not back to NORMAL.
Signed-off-by: Con Kolivas <[email protected]>
---
kernel/sched.c | 52 +++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 39 insertions(+), 13 deletions(-)
Index: linux-ck-dev/kernel/sched.c
===================================================================
--- linux-ck-dev.orig/kernel/sched.c 2006-06-18 15:23:46.000000000 +1000
+++ linux-ck-dev/kernel/sched.c 2006-06-18 15:23:49.000000000 +1000
@@ -3700,19 +3700,44 @@ recheck:
* Allow unprivileged RT tasks to decrease priority:
*/
if (!capable(CAP_SYS_NICE)) {
- /*
- * can't change policy, except between SCHED_NORMAL
- * and SCHED_BATCH:
- */
- if (SCHED_RT(policy) && policy != p->policy &&
- !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
- return -EPERM;
- /* can't increase priority */
- if (SCHED_RT(policy) &&
- param->sched_priority > p->rt_priority &&
- param->sched_priority >
- p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
- return -EPERM;
+ if (SCHED_RT(policy)) {
+ /*
+ * can't change policy to a realtime policy
+ */
+ if (policy != p->policy &&
+ !p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
+ return -EPERM;
+ /* can't increase priority */
+ if (param->sched_priority > p->rt_priority &&
+ param->sched_priority >
+ p->signal->rlim[RLIMIT_RTPRIO].rlim_cur)
+ return -EPERM;
+ } else {
+ switch (p->policy) {
+ /*
+ * Can only downgrade policies but not back to
+ * SCHED_NORMAL
+ */
+ case SCHED_ISO:
+ if (policy == SCHED_ISO)
+ goto out;
+ if (policy == SCHED_NORMAL)
+ return -EPERM;
+ break;
+ case SCHED_BATCH:
+ if (policy == SCHED_BATCH)
+ goto out;
+ if (policy != SCHED_IDLEPRIO)
+ return -EPERM;
+ break;
+ case SCHED_IDLEPRIO:
+ if (policy == SCHED_IDLEPRIO)
+ goto out;
+ return -EPERM;
+ default:
+ break;
+ }
+ }
/* can't change other user's priorities */
if ((current->euid != p->euid) &&
(current->euid != p->uid))
@@ -3756,6 +3781,7 @@ recheck:
preempt(p, rq);
}
task_rq_unlock(rq, &flags);
+out:
return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);
--
-ck
-
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