linux-kernel - [PATCH 4/6] sched/core: Add permission checks for setting the latency

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Date:   Fri, 11 Mar 2022 17:14:04 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, linux-kernel@...r.kernel.org, parth@...ux.ibm.com
Cc:     qais.yousef@....com, chris.hyser@...cle.com,
        pkondeti@...eaurora.org, valentin.schneider@....com,
        patrick.bellasi@...bug.net, David.Laight@...lab.com,
        pjt@...gle.com, pavel@....cz, tj@...nel.org,
        dhaval.giani@...cle.com, qperret@...gle.com,
        tim.c.chen@...ux.intel.com,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 4/6] sched/core: Add permission checks for setting the latency_nice value

From: Parth Shah <parth@...ux.ibm.com>

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@...ux.ibm.com>
[rebase]
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3edba1a38ecb..8f8b102a75c4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7360,6 +7360,10 @@ 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