[PATCH v2] sched/rt: fix the case where sched_rt_period_us is negative

[Yajun Deng]

The proc_dointvec() is for integer, but sysctl_sched_rt_period is a
unsigned integer, proc_dointvec() would convert negative number into
positive number. So both proc_dointvec() and sched_rt_global_validate()
aren't return error even if we set a negative number.

Use proc_dointvec_minmax() instead of proc_dointvec() and use extra1
limit the minimum value for sched_rt_period_us/sched_rt_runtime_us.

Fixes: 391e43da797a ("sched: Move all scheduler bits into kernel/sched/")
Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
---
 kernel/sched/rt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index b491a0f8c25d..3add32679885 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",
@@ -2959,9 +2962,6 @@ 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 +2992,7 @@ 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();
-- 
2.25.1