[PATCH v4 4/8] sched/core: Add permission checks for setting the latency_nice value

[Vincent Guittot]

From: Parth Shah <parth@xxxxxxxxxxxxx>

Since the latency_nice uses the similar infrastructure as NICE, use the
already existing CAP_SYS_NICE security checks for the latency_nice. This
should return -EPERM for the non-root user when trying to set the task
latency_nice value to any lower than the current value.

Signed-off-by: Parth Shah <parth@xxxxxxxxxxxxx>
[rebase]
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2015e7d1f8b2..3c79c5419d1b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7444,6 +7444,10 @@ static int __sched_setscheduler(struct task_struct *p,
 			return -EINVAL;
 		if (attr->sched_latency_nice < MIN_LATENCY_NICE)
 			return -EINVAL;
+		/* Use the same security checks as NICE */
+		if (attr->sched_latency_nice < p->latency_nice &&
+		    !capable(CAP_SYS_NICE))
+			return -EPERM;
 	}
 
 	if (pi)
-- 
2.17.1