linux-kernel - [PATCH] sched/fair: Null terminate buffer when updating tunable

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210927114635.GH3959@techsingularity.net>
Date:   Mon, 27 Sep 2021 12:46:35 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
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 <mgorman@...hsingularity.net>
---
 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;