From e885e6725cd479326ef94692fcfd0d5090d71fde Mon Sep 17 00:00:00 2001 From: Sultan Alsawaf Date: Fri, 3 May 2019 00:34:19 -0700 Subject: [PATCH] qos: Don't allow userspace to impose restrictions on CPU idle levels Giving userspace intimate control over CPU latency requirements is nonsense. Userspace can't even stop itself from being preempted, so there's no reason for it to have access to a mechanism primarily used to eliminate CPU delays on the order of microseconds. Remove userspace's ability to send pm_qos requests so that it can't hurt power consumption. Signed-off-by: Sultan Alsawaf --- kernel/power/qos.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/power/qos.c b/kernel/power/qos.c index e6eceb0aa496..d99360051582 100644 --- a/kernel/power/qos.c +++ b/kernel/power/qos.c @@ -868,6 +868,9 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf, s32 value; struct pm_qos_request *req; + /* Don't let userspace impose restrictions on CPU idle levels */ + return count; + if (count == sizeof(s32)) { if (copy_from_user(&value, buf, sizeof(s32))) return -EFAULT;