Re: [PATCH v2] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

From: chris hyser
Date: Tue Apr 04 2023 - 14:36:35 EST


On 4/4/23 11:32, Chen Yu wrote:
On 2023-03-30 at 11:07:57 -0400, chris hyser wrote:
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 | 52 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..b5fc7e250128 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -278,6 +278,56 @@ 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)
+{
+ int err;
+ char buf[16];
+ unsigned int scan_size;
+
+ if (cnt > 15)
+ cnt = 15;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+ buf[cnt] = '\0';
+
+ err = kstrtouint(buf, 10, &scan_size);
While testing the code, it is found that there is a
kstrtouint_from_user() could do the above. Not sure
if it is worthy to use that?

Yes, putting this in results in cleaner code. Thanks.

I just sent a v3 with this change.

-chrish


thanks,
Chenyu