[PATCH] timer: fix timer_migration to accept only 0 and 1

[PATCH] timer: fix timer_migration to accept only 0 and 1

[Myungho Jung]

Error is not shown by setting invalid value to timer_migration. Valid
values for timer_migration should be restricted to 0 and 1. Testcase for
this bug is ltp/runpwtests06.

Signed-off-by: Myungho Jung <mhjungk@gmail.com>
---
 kernel/sysctl.c     | 2 ++
 kernel/time/timer.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8c8714f..21343d1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1176,6 +1176,8 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= timer_migration_handler,
+		.extra1		= &zero,
+		.extra2		= &one,
 	},
 #endif
 #ifdef CONFIG_BPF_SYSCALL
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1dc0256..cc6b6bd 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -241,7 +241,7 @@ int timer_migration_handler(struct ctl_table *table, int write,
 	int ret;
 
 	mutex_lock(&mutex);
-	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	if (!ret && write)
 		timers_update_migration(false);
 	mutex_unlock(&mutex);
-- 
2.7.4

Re: [PATCH] timer: fix timer_migration to accept only 0 and 1

[Thomas Gleixner]

On Wed, 19 Apr 2017, Myungho Jung wrote:

> Error is not shown by setting invalid value to timer_migration. Valid
> values for timer_migration should be restricted to 0 and 1. Testcase for
> this bug is ltp/runpwtests06.

While I agree with the change, I disagree with the changelog. Where is the bug?

The timer code checks for timer_migration != 0 resp. == 0. So as long as
the value is != 0 it's enabled, if it's 0 it is disabled.

It's a correctness issue that we treat a sysctl which is basically a
boolean as such. Ideally we'd have: proc_doboolvec() for such cases and
convert all similar sysctls over to that.

Thanks,

	tglx

[tip:timers/core] timer/sysclt: Restrict timer migration sysctl values to 0 and 1

[tip-bot for Myungho Jung]

Commit-ID:  b94bf594cf8ed67cdd0439e70fa939783471597a
Gitweb:     http://git.kernel.org/tip/b94bf594cf8ed67cdd0439e70fa939783471597a
Author:     Myungho Jung <mhjungk@gmail.com>
AuthorDate: Wed, 19 Apr 2017 15:24:50 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 20 Apr 2017 14:56:59 +0200

timer/sysclt: Restrict timer migration sysctl values to 0 and 1

timer_migration sysctl acts as a boolean switch, so the allowed values
should be restricted to 0 and 1.

Add the necessary extra fields to the sysctl table entry to enforce that.

[ tglx: Rewrote changelog ]

Signed-off-by: Myungho Jung <mhjungk@gmail.com>
Link: http://lkml.kernel.org/r/1492640690-3550-1-git-send-email-mhjungk@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 kernel/sysctl.c     | 2 ++
 kernel/time/timer.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index acf0a5a..0863769 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1176,6 +1176,8 @@ static struct ctl_table kern_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= timer_migration_handler,
+		.extra1		= &zero,
+		.extra2		= &one,
 	},
 #endif
 #ifdef CONFIG_BPF_SYSCALL
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1dc0256..cc6b6bd 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -241,7 +241,7 @@ int timer_migration_handler(struct ctl_table *table, int write,
 	int ret;
 
 	mutex_lock(&mutex);
-	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	if (!ret && write)
 		timers_update_migration(false);
 	mutex_unlock(&mutex);

Re: [PATCH] timer: fix timer_migration to accept only 0 and 1

[Myungho Jung]

On Thu, Apr 20, 2017 at 02:53:26PM +0200, Thomas Gleixner wrote:
> On Wed, 19 Apr 2017, Myungho Jung wrote:
> 
> > Error is not shown by setting invalid value to timer_migration. Valid
> > values for timer_migration should be restricted to 0 and 1. Testcase for
> > this bug is ltp/runpwtests06.
> 
> While I agree with the change, I disagree with the changelog. Where is the bug?
> 
> The timer code checks for timer_migration != 0 resp. == 0. So as long as
> the value is != 0 it's enabled, if it's 0 it is disabled.
> 
> It's a correctness issue that we treat a sysctl which is basically a
> boolean as such. Ideally we'd have: proc_doboolvec() for such cases and
> convert all similar sysctls over to that.
> 
> Thanks,
> 
> 	tglx
I understood. I'll resubmit the patch after fixing log.

Thanks,
Myungho

Re: [PATCH] timer: fix timer_migration to accept only 0 and 1

[Thomas Gleixner]

On Thu, 20 Apr 2017, Myungho Jung wrote:
> I understood. I'll resubmit the patch after fixing log.

I recommend to check your inbox first.

Thanks,

	tglx

Re: [PATCH] timer: fix timer_migration to accept only 0 and 1

[Myungho Jung]

On Thu, Apr 20, 2017 at 07:45:49PM +0200, Thomas Gleixner wrote:
> On Thu, 20 Apr 2017, Myungho Jung wrote:
> > I understood. I'll resubmit the patch after fixing log.
> 
> I recommend to check your inbox first.
> 
> Thanks,
> 
> 	tglx
Yes, I confirmed a message from tip-bot. I'll refer to it.

Thanks,
Myungho