linux-kernel - [PATCH] sched/rt: fix the case where sched_rt_period

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Date:   Wed, 11 May 2022 19:21:40 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org, Yajun Deng <yajun.deng@...ux.dev>
Subject: [PATCH] sched/rt: fix the case where sched_rt_period_us is non-positive

The proc_dointvec() in sched_rt_handler() is for integer, but
sysctl_sched_rt_period is a unsigned integer. sched_rt_handler() would
cover a non-positive number to positive number, so both proc_dointvec()
and sched_rt_global_validate() aren't return error when we set a
non-positive number.

Use proc_dointvec_minmax() instead of proc_dointvec(), and add extra
for sched_rt_period_us/sched_rt_runtime_us/sched_rr_timeslice_ms.

Fixes: 391e43da797a ("sched: Move all scheduler bits into kernel/sched/")
Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
---
 kernel/sched/rt.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index b491a0f8c25d..f20389aa6731 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -37,6 +37,7 @@ static struct ctl_table sched_rt_sysctls[] = {
 		.maxlen         = sizeof(unsigned int),
 		.mode           = 0644,
 		.proc_handler   = sched_rt_handler,
+		.extra1		= SYSCTL_ONE,
 	},
 	{
 		.procname       = "sched_rt_runtime_us",
@@ -44,6 +45,8 @@ static struct ctl_table sched_rt_sysctls[] = {
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = sched_rt_handler,
+		.extra1		= SYSCTL_NEG_ONE,
+		.extra2		= (void *)&sysctl_sched_rt_period,
 	},
 	{
 		.procname       = "sched_rr_timeslice_ms",
@@ -51,6 +54,7 @@ static struct ctl_table sched_rt_sysctls[] = {
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = sched_rr_handler,
+		.extra1		= SYSCTL_ONE,
 	},
 	{}
 };
@@ -2959,9 +2963,6 @@ static int sched_rt_global_constraints(void)
 #ifdef CONFIG_SYSCTL
 static int sched_rt_global_validate(void)
 {
-	if (sysctl_sched_rt_period <= 0)
-		return -EINVAL;
-
 	if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
 		((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
 		 ((u64)sysctl_sched_rt_runtime *
@@ -2992,7 +2993,7 @@ static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
 	old_period = sysctl_sched_rt_period;
 	old_runtime = sysctl_sched_rt_runtime;
 
-	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
 	if (!ret && write) {
 		ret = sched_rt_global_validate();
@@ -3027,14 +3028,13 @@ static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
 	static DEFINE_MUTEX(mutex);
 
 	mutex_lock(&mutex);
-	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	/*
 	 * Make sure that internally we keep jiffies.
 	 * Also, writing zero resets the timeslice to default:
 	 */
 	if (!ret && write) {
 		sched_rr_timeslice =
-			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
 			msecs_to_jiffies(sysctl_sched_rr_timeslice);
 	}
 	mutex_unlock(&mutex);
-- 
2.25.1