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Subject: Re: [PATCH v4 4/4] sched/core: Add permission checks for setting the
 latency_nice value
To:     Parth Shah <parth@linux.ibm.com>, linux-kernel@vger.kernel.org
Cc:     peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, qais.yousef@arm.com,
        patrick.bellasi@matbug.net, valentin.schneider@arm.com,
        David.Laight@ACULAB.COM, pjt@google.com, pavel@ucw.cz,
        tj@kernel.org, dhaval.giani@oracle.com, qperret@google.com,
        tim.c.chen@linux.intel.com
References: <20200224085918.16955-1-parth@linux.ibm.com>
 <20200224085918.16955-5-parth@linux.ibm.com>
From:   chris hyser <chris.hyser@oracle.com>
Message-ID: <6fb7926e-c8bb-e4a0-c527-feb38c948716@oracle.com>
Date:   Mon, 24 Feb 2020 18:08:10 -0500
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On 2/24/20 3:59 AM, Parth Shah wrote:
> 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@linux.ibm.com>

Reviewed-by: Chris Hyser <chris.hyser@oracle.com>

> ---
>   kernel/sched/core.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index e1dc536d4ca3..f883e1d3cd10 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4887,6 +4887,10 @@ 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 &&
> +		    !can_nice(p, attr->sched_latency_nice))
> +			return -EPERM;
>   	}
>   
>   	if (pi)
>