From d915bc7c0d43424a6e0b7e085aab94b8f214c98c Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@techsingularity.net>
Date: Mon, 27 Sep 2021 12:46:35 +0100
Subject: [PATCH] sched/fair: Null terminate buffer when updating
tunable_scaling
References: bsc#1189999 (Scheduler functional and performance backports) stable-5.14.10
Patch-mainline: v5.15
Git-commit: 703066188f63d66cc6b9d678e5b5ef1213c5938e
This patch null-terminates the temporary buffer in sched_scaling_write()
so kstrtouint() does not return failure and checks the value is valid.
Before:
$ cat /sys/kernel/debug/sched/tunable_scaling
1
$ echo 0 > /sys/kernel/debug/sched/tunable_scaling
-bash: echo: write error: Invalid argument
$ cat /sys/kernel/debug/sched/tunable_scaling
1
After:
$ cat /sys/kernel/debug/sched/tunable_scaling
1
$ echo 0 > /sys/kernel/debug/sched/tunable_scaling
$ cat /sys/kernel/debug/sched/tunable_scaling
0
$ echo 3 > /sys/kernel/debug/sched/tunable_scaling
-bash: echo: write error: Invalid argument
Fixes: 8a99b6833c88 ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210927114635.GH3959@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/sched/debug.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 7e08e3d947c2..2c879cd02a5f 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -173,16 +173,22 @@ static ssize_t sched_scaling_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char buf[16];
+ unsigned int scaling;
if (cnt > 15)
cnt = 15;
if (copy_from_user(&buf, ubuf, cnt))
return -EFAULT;
+ buf[cnt] = '\0';
- if (kstrtouint(buf, 10, &sysctl_sched_tunable_scaling))
+ if (kstrtouint(buf, 10, &scaling))
return -EINVAL;
+ if (scaling >= SCHED_TUNABLESCALING_END)
+ return -EINVAL;
+
+ sysctl_sched_tunable_scaling = scaling;
if (sched_update_scaling())
return -EINVAL;