Commit 97891bbf authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'sched-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fix from Thomas Gleixner:
 "A single scheduler fix to ensure that there is no stale KASAN shadow
  state left on the idle task's stack when a CPU is brought up after it
  was brought down before"

* tag 'sched-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/scs: Reset task stack state in bringup_cpu()
parents 1ed1d3a3 dce1ca05

kernel/cpu.c

+7 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/smpboot.h>

#include <linux/relay.h>

#include <linux/slab.h>

#include <linux/scs.h>

#include <linux/percpu-rwsem.h>

#include <linux/cpuset.h>
@@ -587,6 +588,12 @@ static int bringup_cpu(unsigned int cpu) 
	struct task_struct *idle = idle_thread_get(cpu);

	int ret;



	/*

	 * Reset stale stack state from the last time this CPU was online.

	 */

	scs_task_reset(idle);

	kasan_unpoison_task_stack(idle);



	/*

	 * Some architectures have to walk the irq descriptors to

	 * setup the vector space for the cpu which comes online.

kernel/sched/core.c

+0 −4
Original line number Diff line number Diff line
@@ -8619,9 +8619,6 @@ void __init init_idle(struct task_struct *idle, int cpu) 
	idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY;

	kthread_set_per_cpu(idle, cpu);



	scs_task_reset(idle);

	kasan_unpoison_task_stack(idle);



#ifdef CONFIG_SMP

	/*

	 * It's possible that init_idle() gets called multiple times on a task,
@@ -8777,7 +8774,6 @@ void idle_task_exit(void) 
		finish_arch_post_lock_switch();

	}



	scs_task_reset(current);

	/* finish_cpu(), as ran on the BP, will clean up the active_mm state */

}