2021-09-27 11:48:40

by Mel Gorman

Subject: [PATCH] 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: 8a99b6833c88 ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: Mel Gorman <[email protected]>
---
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 49716228efb4..17a653b67006 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;

2021-09-27 16:54:47

by Vincent Guittot

Subject: Re: [PATCH] sched/fair: Null terminate buffer when updating tunable_scaling

On Mon, 27 Sept 2021 at 13:46, Mel Gorman <[email protected]> wrote:
>
> 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 <[email protected]>

Acked-by: Vincent Guittot <[email protected]>

> ---
> 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 49716228efb4..17a653b67006 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;
>

2021-10-01 12:12:31

by tip-bot2 for Alexey Makhalov

Subject: [tip: sched/urgent] sched/fair: Null terminate buffer when updating tunable_scaling

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID: 703066188f63d66cc6b9d678e5b5ef1213c5938e
Gitweb: https://git.kernel.org/tip/703066188f63d66cc6b9d678e5b5ef1213c5938e
Author: Mel Gorman <[email protected]>
AuthorDate: Mon, 27 Sep 2021 12:46:35 +01:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Fri, 01 Oct 2021 13:57:57 +02:00

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: 8a99b6833c88 ("sched: Move SCHED_DEBUG sysctl to debugfs")
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Vincent Guittot <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
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 4971622..17a653b 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;