[PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

From: Chris Hyser
Date: Wed Mar 29 2023 - 12:26:34 EST


From: chris hyser <chris.hyser@xxxxxxxxxx>

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.

Signed-off-by: Chris Hyser <chris.hyser@xxxxxxxxxx>
---
kernel/sched/debug.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..dfd0fe6123ec 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -278,6 +278,54 @@ static const struct file_operations sched_dynamic_fops = {

#endif /* CONFIG_PREEMPT_DYNAMIC */

+#ifdef CONFIG_NUMA_BALANCING
+
+static ssize_t sched_numa_scan_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[16];
+ unsigned int scan_size;
+
+ if (cnt > 15)
+ cnt = 15;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+ buf[cnt] = '\0';
+
+ if (kstrtouint(buf, 10, &scan_size))
+ return -EINVAL;
+
+ if (!scan_size)
+ return -EINVAL;
+
+ sysctl_numa_balancing_scan_size = scan_size;
+
+ *ppos += cnt;
+ return cnt;
+}
+
+static int sched_numa_scan_show(struct seq_file *m, void *v)
+{
+ seq_printf(m, "%d\n", sysctl_numa_balancing_scan_size);
+ return 0;
+}
+
+static int sched_numa_scan_open(struct inode *inode, struct file *filp)
+{
+ return single_open(filp, sched_numa_scan_show, NULL);
+}
+
+static const struct file_operations sched_numa_scan_fops = {
+ .open = sched_numa_scan_open,
+ .write = sched_numa_scan_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+#endif /* CONFIG_NUMA_BALANCING */
+
__read_mostly bool sched_debug_verbose;

static const struct seq_operations sched_debug_sops;
@@ -332,7 +380,7 @@ 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_file("scan_size_mb", 0644, numa, NULL, &sched_numa_scan_fops);
debugfs_create_u32("hot_threshold_ms", 0644, numa, &sysctl_numa_balancing_hot_threshold);
#endif

--
2.31.1