linux-kernel - [PATCH 4/4] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan

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Message-Id: <20230530194012.44411-5-chris.hyser@oracle.com>
Date:   Tue, 30 May 2023 15:40:12 -0400
From:   chris hyser <chris.hyser@...cle.com>
To:     chris.hyser@...cle.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, gregkh@...uxfoundation.org,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH 4/4] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

Commit 6419265899d9 ("sched/fair: Fix division by zero
sysctl_numa_balancing_scan_size") prevented a divide by zero by using
sysctl mechanisms to return EINVAL for a sysctl_numa_balancing_scan_size
value of zero. When moved from a sysctl to a debugfs file, this checking
was lost.

This patch puts zero checking back in place using the debugfs minmax
checking mechanism.

Cc: stable@...r.kernel.org
Fixes: 8a99b6833c88 ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: Chris Hyser <chris.hyser@...cle.com>
---
 kernel/sched/debug.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 066ff1c8ae4e..b9e53ecc539a 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -216,6 +216,13 @@ static const struct file_operations sched_scaling_fops = {
 
 #endif /* SMP */
 
+#ifdef CONFIG_NUMA_BALANCING
+
+/* prevent divide by zero */
+DEBUGFS_MIN_ATTRIBUTES(scan_size_mb_params, &sysctl_numa_balancing_scan_size, 1);
+
+#endif /* CONFIG_NUMA_BALANCING */
+
 #ifdef CONFIG_PREEMPT_DYNAMIC
 
 static ssize_t sched_dynamic_write(struct file *filp, const char __user *ubuf,
@@ -371,7 +378,7 @@ static __init int sched_init_debug(void)
 	debugfs_create_u32("scan_delay_ms", 0644, numa, &sysctl_numa_balancing_scan_delay);
 	debugfs_create_u32("scan_period_min_ms", 0644, numa, &sysctl_numa_balancing_scan_period_min);
 	debugfs_create_u32("scan_period_max_ms", 0644, numa, &sysctl_numa_balancing_scan_period_max);
-	debugfs_create_u32("scan_size_mb", 0644, numa, &sysctl_numa_balancing_scan_size);
+	debugfs_create_u32_minmax("scan_size_mb", 0644, numa, &scan_size_mb_params);
 	debugfs_create_u32("hot_threshold_ms", 0644, numa, &sysctl_numa_balancing_hot_threshold);
 #endif
 
-- 
2.31.1