From 9c95e7319ba98585ebb6d304eca2d56f401ed70c Mon Sep 17 00:00:00 2001 From: Hiroshi Shimamoto Date: Wed, 19 Sep 2007 23:34:46 +0200 Subject: [PATCH] sched: fix invalid sched_class use When using rt_mutex, a NULL pointer dereference is occurred at enqueue_task_rt. Here is a scenario; 1) there are two threads, the thread A is fair_sched_class and thread B is rt_sched_class. 2) Thread A is boosted up to rt_sched_class, because the thread A has a rt_mutex lock and the thread B is waiting the lock. 3) At this time, when thread A create a new thread C, the thread C has a rt_sched_class. 4) When doing wake_up_new_task() for the thread C, the priority of the thread C is out of the RT priority range, because the normal priority of thread A is not the RT priority. It makes data corruption by overflowing the rt_prio_array. The new thread C should be fair_sched_class. The new thread should be valid scheduler class before queuing. This patch fixes to set the suitable scheduler class. Signed-off-by: Hiroshi Shimamoto Signed-off-by: Ingo Molnar Signed-off-by: Peter Zijlstra --- kernel/sched.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched.c b/kernel/sched.c index 63e0971c8fbb..6107a0cd6325 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1682,6 +1682,11 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags) p->prio = effective_prio(p); + if (rt_prio(p->prio)) + p->sched_class = &rt_sched_class; + else + p->sched_class = &fair_sched_class; + if (!p->sched_class->task_new || !sysctl_sched_child_runs_first || (clone_flags & CLONE_VM) || task_cpu(p) != this_cpu || !current->se.on_rq) {