This is a note to let you know that I've just added the patch titled sched/scs: Reset the shadow stack when idle_task_exit to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sched-scs-reset-the-shadow-stack-when-idle_task_exit.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit db4189654eebf1e8df013822135ee7e73225bdba Author: Woody Lin <woodylin@xxxxxxxxxx> Date: Tue Oct 12 16:35:21 2021 +0800 sched/scs: Reset the shadow stack when idle_task_exit [ Upstream commit 63acd42c0d4942f74710b11c38602fb14dea7320 ] Commit f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled") removed the init_idle() call from idle_thread_get(). This was the sole call-path on hotplug that resets the Shadow Call Stack (scs) Stack Pointer (sp). Not resetting the scs-sp leads to scs overflow after enough hotplug cycles. Therefore add an explicit scs_task_reset() to the hotplug code to make sure the scs-sp does get reset on hotplug. Fixes: f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled") Signed-off-by: Woody Lin <woodylin@xxxxxxxxxx> [peterz: Changelog] Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx> Link: https://lore.kernel.org/r/20211012083521.973587-1-woodylin@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 399c37c95392..e165d28cf73b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8495,6 +8495,7 @@ 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 */ }