Commit 70306618 authored by Mel Gorman's avatar Mel Gorman Committed by Peter Zijlstra
Browse files

sched/fair: Null terminate buffer when updating tunable_scaling 



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: 8a99b683 ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210927114635.GH3959@techsingularity.net
parent 2630cde2

kernel/sched/debug.c

+7 −1
Original line number Diff line number Diff line
@@ -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;