linux-kernel - [PATCH v5 4/4] sched/core: Add permission checks for setting the latency

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Message-Id: <20200228090755.22829-5-parth@linux.ibm.com>
Date:   Fri, 28 Feb 2020 14:37:55 +0530
From:   Parth Shah <parth@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, qais.yousef@....com,
        chris.hyser@...cle.com, pkondeti@...eaurora.org,
        patrick.bellasi@...bug.net, valentin.schneider@....com,
        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
Subject: [PATCH v5 4/4] sched/core: Add permission checks for setting the latency_nice value

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>
Reviewed-by: Chris Hyser <chris.hyser@...cle.com>
---
 kernel/sched/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cd1fb9c8be26..564b3a2036d4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4875,6 +4875,10 @@ 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)
-- 
2.17.2