From dae51f56204d33444f61d9e7af3ee70aef55daa4 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 15 Nov 2007 20:57:40 +0100 Subject: [PATCH] sched: fix SCHED_FIFO tasks & FAIR_GROUP_SCHED Suppose that the SCHED_FIFO task does switch_uid(new_user); Now, p->se.cfs_rq and p->se.parent both point into the old user_struct->tg because sched_move_task() doesn't call set_task_cfs_rq() for !fair_sched_class case. Suppose that old user_struct/task_group is freed/reused, and the task does sched_setscheduler(SCHED_NORMAL); __setscheduler() sets fair_sched_class, but doesn't update ->se.cfs_rq/parent which point to the freed memory. This means that check_preempt_wakeup() doing while (!is_same_group(se, pse)) { se = parent_entity(se); pse = parent_entity(pse); } may OOPS in a similar way if rq->curr or p did something like above. Perhaps we need something like the patch below, note that __setscheduler() can't do set_task_cfs_rq(). Signed-off-by: Oleg Nesterov Signed-off-by: Ingo Molnar --- kernel/sched.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched.c b/kernel/sched.c index 908335e1781a..d62b759753f3 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7087,8 +7087,10 @@ void sched_move_task(struct task_struct *tsk) rq = task_rq_lock(tsk, &flags); - if (tsk->sched_class != &fair_sched_class) + if (tsk->sched_class != &fair_sched_class) { + set_task_cfs_rq(tsk); goto done; + } update_rq_clock(rq); -- 2.30.2