[PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Zhiqiang Liu]

From: Zhiqiang Liu <liuzhiqiang26@huawei.com>

In proc_dointvec_jiffies func, the write value is only checked
whether it is larger than INT_MAX. If the write value is less
than zero, it can also be successfully writen in the data.

However, in some scenarios, users would adopt the data to
set timers or check whether time is expired. Generally, the data
will be cast to an unsigned type variable, then the negative data
becomes a very large unsigned value, which leads to long waits
or other unpredictable problems.

Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
min/max write value, which is similar to the proc_dointvec_minmax func.

Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Reported-by: Qiang Ning <ningqiang1@huawei.com>
Reviewed-by: Jie Liu <liujie165@huawei.com>
---
 include/linux/sysctl.h |  2 ++
 kernel/sysctl.c        | 44 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index b769ecf..8bde8a0 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -53,6 +53,8 @@ extern int proc_douintvec_minmax(struct ctl_table *table, int write,
 				 loff_t *ppos);
 extern int proc_dointvec_jiffies(struct ctl_table *, int,
 				 void __user *, size_t *, loff_t *);
+extern int proc_dointvec_jiffies_minmax(struct ctl_table *, int,
+				 void __user *, size_t *, loff_t *);
 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
 					void __user *, size_t *, loff_t *);
 extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c9ec050..8e1eb59 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2967,10 +2967,15 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp,
 					 int *valp,
 					 int write, void *data)
 {
+	struct do_proc_dointvec_minmax_conv_param *param = data;
+
 	if (write) {
 		if (*lvalp > INT_MAX / HZ)
 			return 1;
 		*valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ);
+		if ((param->min && (*param->min)*HZ > *valp) ||
+		    (param->max && (*param->max)*HZ < *valp))
+			return -EINVAL;
 	} else {
 		int val = *valp;
 		unsigned long lval;
@@ -3053,7 +3058,37 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
 			  void __user *buffer, size_t *lenp, loff_t *ppos)
 {
     return do_proc_dointvec(table,write,buffer,lenp,ppos,
-		    	    do_proc_dointvec_jiffies_conv,NULL);
+			    do_proc_dointvec_jiffies_conv, NULL);
+}
+
+/**
+ * proc_dointvec_jiffies_minmax - read a vector of integers as seconds with min/max values
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ * The values read are assumed to be in seconds, and are converted into
+ * jiffies.
+ *
+ * This routine will ensure the values are within the range specified by
+ * table->extra1 (min) and table->extra2 (max).
+ *
+ * Returns 0 on success or -EINVAL on write when the range check fails.
+ */
+int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
+			  void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct do_proc_dointvec_minmax_conv_param param = {
+		.min = (int *) table->extra1,
+		.max = (int *) table->extra2,
+	};
+
+	return do_proc_dointvec(table, write, buffer, lenp, ppos,
+				do_proc_dointvec_jiffies_conv, &param);
 }

 /**
@@ -3301,6 +3336,12 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
 	return -ENOSYS;
 }

+int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
+		    void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec_userhz_jiffies(struct ctl_table *table, int write,
 		    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3359,6 +3400,7 @@ static int proc_dointvec_minmax_bpf_stats(struct ctl_table *table, int write,
 EXPORT_SYMBOL(proc_dointvec);
 EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);
+EXPORT_SYMBOL(proc_dointvec_jiffies_minmax);
 EXPORT_SYMBOL(proc_dointvec_minmax);
 EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
 EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
-- 
1.8.3.1

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Zhiqiang Liu]

Friendly ping...

> From: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> 
> In proc_dointvec_jiffies func, the write value is only checked
> whether it is larger than INT_MAX. If the write value is less
> than zero, it can also be successfully writen in the data.
> 
> However, in some scenarios, users would adopt the data to
> set timers or check whether time is expired. Generally, the data
> will be cast to an unsigned type variable, then the negative data
> becomes a very large unsigned value, which leads to long waits
> or other unpredictable problems.
> 
> Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
> min/max write value, which is similar to the proc_dointvec_minmax func.
> 
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> Reported-by: Qiang Ning <ningqiang1@huawei.com>
> Reviewed-by: Jie Liu <liujie165@huawei.com>
> ---
>  include/linux/sysctl.h |  2 ++
>  kernel/sysctl.c        | 44 +++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index b769ecf..8bde8a0 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -53,6 +53,8 @@ extern int proc_douintvec_minmax(struct ctl_table *table, int write,
>  				 loff_t *ppos);
>  extern int proc_dointvec_jiffies(struct ctl_table *, int,
>  				 void __user *, size_t *, loff_t *);
> +extern int proc_dointvec_jiffies_minmax(struct ctl_table *, int,
> +				 void __user *, size_t *, loff_t *);
>  extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
>  					void __user *, size_t *, loff_t *);
>  extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index c9ec050..8e1eb59 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2967,10 +2967,15 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp,
>  					 int *valp,
>  					 int write, void *data)
>  {
> +	struct do_proc_dointvec_minmax_conv_param *param = data;
> +
>  	if (write) {
>  		if (*lvalp > INT_MAX / HZ)
>  			return 1;
>  		*valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ);
> +		if ((param->min && (*param->min)*HZ > *valp) ||
> +		    (param->max && (*param->max)*HZ < *valp))
> +			return -EINVAL;
>  	} else {
>  		int val = *valp;
>  		unsigned long lval;
> @@ -3053,7 +3058,37 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
>  			  void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
>      return do_proc_dointvec(table,write,buffer,lenp,ppos,
> -		    	    do_proc_dointvec_jiffies_conv,NULL);
> +			    do_proc_dointvec_jiffies_conv, NULL);
> +}
> +
> +/**
> + * proc_dointvec_jiffies_minmax - read a vector of integers as seconds with min/max values
> + * @table: the sysctl table
> + * @write: %TRUE if this is a write to the sysctl file
> + * @buffer: the user buffer
> + * @lenp: the size of the user buffer
> + * @ppos: file position
> + *
> + * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
> + * values from/to the user buffer, treated as an ASCII string.
> + * The values read are assumed to be in seconds, and are converted into
> + * jiffies.
> + *
> + * This routine will ensure the values are within the range specified by
> + * table->extra1 (min) and table->extra2 (max).
> + *
> + * Returns 0 on success or -EINVAL on write when the range check fails.
> + */
> +int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
> +			  void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	struct do_proc_dointvec_minmax_conv_param param = {
> +		.min = (int *) table->extra1,
> +		.max = (int *) table->extra2,
> +	};
> +
> +	return do_proc_dointvec(table, write, buffer, lenp, ppos,
> +				do_proc_dointvec_jiffies_conv, &param);
>  }
> 
>  /**
> @@ -3301,6 +3336,12 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
>  	return -ENOSYS;
>  }
> 
> +int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
> +		    void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	return -ENOSYS;
> +}
> +
>  int proc_dointvec_userhz_jiffies(struct ctl_table *table, int write,
>  		    void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
> @@ -3359,6 +3400,7 @@ static int proc_dointvec_minmax_bpf_stats(struct ctl_table *table, int write,
>  EXPORT_SYMBOL(proc_dointvec);
>  EXPORT_SYMBOL(proc_douintvec);
>  EXPORT_SYMBOL(proc_dointvec_jiffies);
> +EXPORT_SYMBOL(proc_dointvec_jiffies_minmax);
>  EXPORT_SYMBOL(proc_dointvec_minmax);
>  EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
>  EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
> 

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Zhiqiang Liu]

Friendly ping...

在 2019/4/24 12:04, Zhiqiang Liu 写道:
> 
> Friendly ping...
> 
>> From: Zhiqiang Liu <liuzhiqiang26@huawei.com>
>>
>> In proc_dointvec_jiffies func, the write value is only checked
>> whether it is larger than INT_MAX. If the write value is less
>> than zero, it can also be successfully writen in the data.
>>
>> However, in some scenarios, users would adopt the data to
>> set timers or check whether time is expired. Generally, the data
>> will be cast to an unsigned type variable, then the negative data
>> becomes a very large unsigned value, which leads to long waits
>> or other unpredictable problems.
>>
>> Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
>> min/max write value, which is similar to the proc_dointvec_minmax func.
>>
>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
>> Reported-by: Qiang Ning <ningqiang1@huawei.com>
>> Reviewed-by: Jie Liu <liujie165@huawei.com>
>> ---
>>  include/linux/sysctl.h |  2 ++
>>  kernel/sysctl.c        | 44 +++++++++++++++++++++++++++++++++++++++++++-
>>  2 files changed, 45 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
>> index b769ecf..8bde8a0 100644
>> --- a/include/linux/sysctl.h
>> +++ b/include/linux/sysctl.h
>> @@ -53,6 +53,8 @@ extern int proc_douintvec_minmax(struct ctl_table *table, int write,
>>  				 loff_t *ppos);
>>  extern int proc_dointvec_jiffies(struct ctl_table *, int,
>>  				 void __user *, size_t *, loff_t *);
>> +extern int proc_dointvec_jiffies_minmax(struct ctl_table *, int,
>> +				 void __user *, size_t *, loff_t *);
>>  extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,
>>  					void __user *, size_t *, loff_t *);
>>  extern int proc_dointvec_ms_jiffies(struct ctl_table *, int,
>> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>> index c9ec050..8e1eb59 100644
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -2967,10 +2967,15 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp,
>>  					 int *valp,
>>  					 int write, void *data)
>>  {
>> +	struct do_proc_dointvec_minmax_conv_param *param = data;
>> +
>>  	if (write) {
>>  		if (*lvalp > INT_MAX / HZ)
>>  			return 1;
>>  		*valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ);
>> +		if ((param->min && (*param->min)*HZ > *valp) ||
>> +		    (param->max && (*param->max)*HZ < *valp))
>> +			return -EINVAL;
>>  	} else {
>>  		int val = *valp;
>>  		unsigned long lval;
>> @@ -3053,7 +3058,37 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
>>  			  void __user *buffer, size_t *lenp, loff_t *ppos)
>>  {
>>      return do_proc_dointvec(table,write,buffer,lenp,ppos,
>> -		    	    do_proc_dointvec_jiffies_conv,NULL);
>> +			    do_proc_dointvec_jiffies_conv, NULL);
>> +}
>> +
>> +/**
>> + * proc_dointvec_jiffies_minmax - read a vector of integers as seconds with min/max values
>> + * @table: the sysctl table
>> + * @write: %TRUE if this is a write to the sysctl file
>> + * @buffer: the user buffer
>> + * @lenp: the size of the user buffer
>> + * @ppos: file position
>> + *
>> + * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
>> + * values from/to the user buffer, treated as an ASCII string.
>> + * The values read are assumed to be in seconds, and are converted into
>> + * jiffies.
>> + *
>> + * This routine will ensure the values are within the range specified by
>> + * table->extra1 (min) and table->extra2 (max).
>> + *
>> + * Returns 0 on success or -EINVAL on write when the range check fails.
>> + */
>> +int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
>> +			  void __user *buffer, size_t *lenp, loff_t *ppos)
>> +{
>> +	struct do_proc_dointvec_minmax_conv_param param = {
>> +		.min = (int *) table->extra1,
>> +		.max = (int *) table->extra2,
>> +	};
>> +
>> +	return do_proc_dointvec(table, write, buffer, lenp, ppos,
>> +				do_proc_dointvec_jiffies_conv, &param);
>>  }
>>
>>  /**
>> @@ -3301,6 +3336,12 @@ int proc_dointvec_jiffies(struct ctl_table *table, int write,
>>  	return -ENOSYS;
>>  }
>>
>> +int proc_dointvec_jiffies_minmax(struct ctl_table *table, int write,
>> +		    void __user *buffer, size_t *lenp, loff_t *ppos)
>> +{
>> +	return -ENOSYS;
>> +}
>> +
>>  int proc_dointvec_userhz_jiffies(struct ctl_table *table, int write,
>>  		    void __user *buffer, size_t *lenp, loff_t *ppos)
>>  {
>> @@ -3359,6 +3400,7 @@ static int proc_dointvec_minmax_bpf_stats(struct ctl_table *table, int write,
>>  EXPORT_SYMBOL(proc_dointvec);
>>  EXPORT_SYMBOL(proc_douintvec);
>>  EXPORT_SYMBOL(proc_dointvec_jiffies);
>> +EXPORT_SYMBOL(proc_dointvec_jiffies_minmax);
>>  EXPORT_SYMBOL(proc_dointvec_minmax);
>>  EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
>>  EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
>>
> 
> 
> .
> 

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Kees Cook]

On Wed, May 15, 2019 at 10:53:55PM +0800, Zhiqiang Liu wrote:
> Friendly ping...
> 
> 在 2019/4/24 12:04, Zhiqiang Liu 写道:
> > 
> > Friendly ping...

Hi!

(Please include akpm on CC for next versions of this, as he's likely
the person to take this patch.)

> > 
> >> From: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> >>
> >> In proc_dointvec_jiffies func, the write value is only checked
> >> whether it is larger than INT_MAX. If the write value is less
> >> than zero, it can also be successfully writen in the data.

This appears to be "be design", but I see many "unsigned int" users
that might be tricked into giant values... (for example, see
net/netfilter/nf_conntrack_standalone.c)

Should proc_dointvec_jiffies() just be fixed to disallow negative values
entirely? Looking at the implementation, it seems to be very intentional
about accepting negative values.

However, when I looked through a handful of proc_dointvec_jiffies()
users, it looks like they're all expecting a positive value. Many in the
networking subsystem are, in fact, writing to unsigned long variables,
as I mentioned.

Are there real-world cases of wanting to set a negative jiffie value
via proc_dointvec_jiffies()?

> >>
> >> However, in some scenarios, users would adopt the data to
> >> set timers or check whether time is expired. Generally, the data
> >> will be cast to an unsigned type variable, then the negative data
> >> becomes a very large unsigned value, which leads to long waits
> >> or other unpredictable problems.
> >>
> >> Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
> >> min/max write value, which is similar to the proc_dointvec_minmax func.
> >>
> >> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> >> Reported-by: Qiang Ning <ningqiang1@huawei.com>
> >> Reviewed-by: Jie Liu <liujie165@huawei.com>

If proc_dointvec_jiffies() can't just be fixed, where will the new
function get used? It seems all the "unsigned int" users could benefit.

-- 
Kees Cook

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Zhiqiang Liu]

> On Wed, May 15, 2019 at 10:53:55PM +0800, Zhiqiang Liu wrote:
> 
> (Please include akpm on CC for next versions of this, as he's likely
> the person to take this patch.)
Thanks for your advice. And sorry to reply you so late.

>>>> In proc_dointvec_jiffies func, the write value is only checked
>>>> whether it is larger than INT_MAX. If the write value is less
>>>> than zero, it can also be successfully writen in the data.
> 
> This appears to be "be design", but I see many "unsigned int" users
> that might be tricked into giant values... (for example, see
> net/netfilter/nf_conntrack_standalone.c)
> 
> Should proc_dointvec_jiffies() just be fixed to disallow negative values
> entirely? Looking at the implementation, it seems to be very intentional
> about accepting negative values.
> 
> However, when I looked through a handful of proc_dointvec_jiffies()
> users, it looks like they're all expecting a positive value. Many in the
> networking subsystem are, in fact, writing to unsigned long variables,
> as I mentioned.
> 
I totally agree with you. And I also cannot find an scenario that expects
negative values. Consideing the "negative" scenario may be exist, I add the
proc_dointvec_jiffies_minmax like proc_dointvec_minmax.

> Are there real-world cases of wanting to set a negative jiffie value
> via proc_dointvec_jiffies()?
Until now, I do not find such cases.

>>>>
>>>> Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
>>>> min/max write value, which is similar to the proc_dointvec_minmax func.
>>>>
> 
> If proc_dointvec_jiffies() can't just be fixed, where will the new
> function get used? It seems all the "unsigned int" users could benefit.
> 
I tend to add the proc_dointvec_jiffies_minmax func to provide more choices and
not change the previous use of proc_dointvec_jiffies func.

Thanks for your reply again.

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Zhiqiang Liu]

friendly ping ...

On 2019/6/4 23:27, Zhiqiang Liu wrote:
>> On Wed, May 15, 2019 at 10:53:55PM +0800, Zhiqiang Liu wrote:
>>
>> (Please include akpm on CC for next versions of this, as he's likely
>> the person to take this patch.)
> Thanks for your advice. And sorry to reply you so late.
> 
>>>>> In proc_dointvec_jiffies func, the write value is only checked
>>>>> whether it is larger than INT_MAX. If the write value is less
>>>>> than zero, it can also be successfully writen in the data.
>>
>> This appears to be "be design", but I see many "unsigned int" users
>> that might be tricked into giant values... (for example, see
>> net/netfilter/nf_conntrack_standalone.c)
>>
>> Should proc_dointvec_jiffies() just be fixed to disallow negative values
>> entirely? Looking at the implementation, it seems to be very intentional
>> about accepting negative values.
>>
>> However, when I looked through a handful of proc_dointvec_jiffies()
>> users, it looks like they're all expecting a positive value. Many in the
>> networking subsystem are, in fact, writing to unsigned long variables,
>> as I mentioned.
>>
> I totally agree with you. And I also cannot find an scenario that expects
> negative values. Consideing the "negative" scenario may be exist, I add the
> proc_dointvec_jiffies_minmax like proc_dointvec_minmax.
> 
>> Are there real-world cases of wanting to set a negative jiffie value
>> via proc_dointvec_jiffies()?
> Until now, I do not find such cases.
> 
>>>>>
>>>>> Here, we add a new func, proc_dointvec_jiffies_minmax, to limit the
>>>>> min/max write value, which is similar to the proc_dointvec_minmax func.
>>>>>
>>
>> If proc_dointvec_jiffies() can't just be fixed, where will the new
>> function get used? It seems all the "unsigned int" users could benefit.
>>
> I tend to add the proc_dointvec_jiffies_minmax func to provide more choices and
> not change the previous use of proc_dointvec_jiffies func.
> 
> Thanks for your reply again.
> 
> 
> .
> 

Re: [PATCH next] sysctl: add proc_dointvec_jiffies_minmax to limit the min/max write value

[Luis Chamberlain]

On Tue, Jun 04, 2019 at 11:27:51PM +0800, Zhiqiang Liu wrote:
> > On Wed, May 15, 2019 at 10:53:55PM +0800, Zhiqiang Liu wrote:
> >>>> In proc_dointvec_jiffies func, the write value is only checked
> >>>> whether it is larger than INT_MAX. If the write value is less
> >>>> than zero, it can also be successfully writen in the data.
> > 
> > This appears to be "be design", but I see many "unsigned int" users
> > that might be tricked into giant values... (for example, see
> > net/netfilter/nf_conntrack_standalone.c)
> > 
> > Should proc_dointvec_jiffies() just be fixed to disallow negative values
> > entirely? Looking at the implementation, it seems to be very intentional
> > about accepting negative values.
> > 
> > However, when I looked through a handful of proc_dointvec_jiffies()
> > users, it looks like they're all expecting a positive value. Many in the
> > networking subsystem are, in fact, writing to unsigned long variables,
> > as I mentioned.
> > 
> I totally agree with you. And I also cannot find an scenario that expects
> negative values. Consideing the "negative" scenario may be exist, I add the
> proc_dointvec_jiffies_minmax like proc_dointvec_minmax.

If no negative values exist, and there is no real point to it, then just
rename the existing one and update the docs.

  Luis