Subject: Re: [PATCH v5 1/2] sctp: check the rto_min and rto_max

From: Wang Weidong <[email-masked]>
Date: Mon, 9 Dec 2013 11:28:44 +0800

On 2013/12/9 10:40, Vlad Yasevich wrote:
> On 12/08/2013 09:28 PM, Wang Weidong wrote:
>> On 2013/12/9 10:19, Vlad Yasevich wrote:
>>> On 12/08/2013 08:53 PM, Wang Weidong wrote:
>>>> On 2013/12/8 2:54, Vlad Yasevich wrote:
>>>>> On 12/07/2013 02:17 AM, Wang Weidong wrote:
>>>>>> rto_min should be smaller than rto_max while rto_max should be larger
>>>>>> than rto_min. Add two proc_handler for the checking. Add the check in
>>>>>> sctp_setsockopt_rtoinfo.
>>>>>>
>>>>>> Suggested-by: Vlad Yasevich <[email-masked]>
>>>>>> Signed-off-by: Wang Weidong <[email-masked]>
>>>>>> ---
>>>>>>  include/net/sctp/constants.h |  3 ++
>>>>>>  net/sctp/socket.c            |  5 +++
>>>>>>  net/sctp/sysctl.c            | 73 ++++++++++++++++++++++++++++++++++++++++----
>>>>>>  3 files changed, 75 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
>>>>>> index 2f0a565..d276978 100644
>>>>>> --- a/include/net/sctp/constants.h
>>>>>> +++ b/include/net/sctp/constants.h
>>>>>> @@ -279,6 +279,9 @@ enum { SCTP_MAX_GABS = 16 };
>>>>>>  #define SCTP_RTO_ALPHA          3   /* 1/8 when converted to right shifts. */
>>>>>>  #define SCTP_RTO_BETA           2   /* 1/4 when converted to right shifts. */
>>>>>>  
>>>>>> +#define SCTP_ONE                1        /* 1 ms */
>>>>>> +#define SCTP_TIMER_MAX          86400000 /* ms in one day */
>>>>>> +
>>>>>>  /* Maximum number of new data packets that can be sent in a burst.  */
>>>>>>  #define SCTP_DEFAULT_MAX_BURST		4
>>>>>>  
>>>>>> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
>>>>>> index 72046b9..13411ad 100644
>>>>>> --- a/net/sctp/socket.c
>>>>>> +++ b/net/sctp/socket.c
>>>>>> @@ -2818,6 +2818,11 @@ static int sctp_setsockopt_rtoinfo(struct sock *sk, char __user *optval, unsigne
>>>>>>  	if (copy_from_user(&rtoinfo, optval, optlen))
>>>>>>  		return -EFAULT;
>>>>>>  
>>>>>> +	if (rtoinfo.srto_min < SCTP_ONE ||
>>>>>> +	    rtoinfo.srto_max > SCTP_TIMER_MAX ||
>>>>>> +	    rtoinfo.srto_max < rtoinfo.srto_min)
>>>>>> +		return -EINVAL;
>>>>>> +
>>>>>
>>>>> You can not do the check for srto_min < 1.  The following is the text
>>>>> from the spec:
>>>>>    All times are given in milliseconds.  A value of 0, when modifying
>>>>>    the parameters, indicates that the current value should not be
>>>>>    changed.
>>>>>
>>>> Yes, Your are right, I found it in draft-ietf-tsvwg-sctpsocket-14.txt.
>>>> Thanks.
>>>>
>>>>> So, it is valid for a user to pass in a value of 0.  Also, I am not sure
>>>>> if it makes sense to bind the upper limit here, as well.
>>>>>
>>>>> -vlad
>>>>>
>>>> Here, I am not sure as well. I think it should like what we do to the
>>>> init_net.sctp.rto_max when set larger than timer_max. Just not change the value.
>>>>
>>>
>>> So, the basic reason that sysctl is limited is that it is a default
>>> for all sctp association on the system.  It makes some sense to limit
>>> what the max value here could be.  Limiting it to double suggested
>>> RTO.MAX would only make it 2 minutes and may be insufficient for some
>>> of the high latency low-throughput wireless links.  Making it about an
>>> hour should be fine...  This would be a separate patch though...
>>>
>> Here, you mean that we should use 3600*1000 rather than 86400000? So
>> we should use another patch to fix that after my patchs?
>>
>>> Limiting the user-supplied value is not as appropriate since the
>>> assumption is that user application may know better what it's
>>> requirements are and it is not up to the stack to limit those.  As
>>> long as the user value is withing the usable range (and the kernel
>>> will already knows how and does limit this range), we should not
>>> limit this further.
>>>
>>> -vlad
>>>
>> Agree, So I should check like this:
>> !srto_min || !srto_max || srto_min > srto_max ?
>> And no need to add macros for checking.
> 
> No, I think this would have to be a little more complicated :(
> Remember it's ok to have srto_min == 0 and srto_max == 0.  It just
> means that no change happens.
> 
> You may need to do something like
> 
>   unsigned long rto_max, rto_min;
> 
>   if (rtoinfo.srto_max)
>      rto_max = msecs_to_jiffies(rtoinfo.srto_max);
>   else
>      rto_max = asoc ? asoc->rto_max : sp->rto_max;
> 
>   if (rtoinfo.srto_min)
>      rto_min = msecs_to_jiffies(rtoinfo.srto_min);
>   else
>      rto_min = asoc ? asoc->rto_min : sp->rto_min;
> 
>   if (rto_min > rto_max)
>       return -EINVAL;
> 
>   if (asoc) {
>       asoc->rto_min = rto_min;
>       asoc->rto_max = rto_max;
>    ...
>    etc....
> 
> This way we make sure that the user that supplied just rto_min or just
> rto_max didn't set them so that min > max.
> 
> -vlad

Hi vald,

I found that we had checked the value of 0 in sctp_setsockopt_rtoinfo.
So I only do this:

if (asoc) {
+	if (msecs_to_jiffies(rtoinfo.srto_min) >
+                   msecs_to_jiffies(rtoinfo.srto_max))
+                       return -EINVAL;
	...
} else {
	...
+	if (rtoinfo.srto_min > rtoinfo.srto_max)
+                       return -EINVAL;
	...
}

There because we set value to asoc and sp is not same. So I add the
check into two path.

Regards.
Wang

>>
>> Thanks.
>>
>>>>
>>>> Regards.
>>>> Wang
>>>>
>>>>>>  	asoc = sctp_id2assoc(sk, rtoinfo.srto_assoc_id);
>>>>>>  
>>>>>>  	/* Set the values to the specific association */
>>>>>> diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
>>>>>> index 6b36561..33c56c6 100644
>>>>>> --- a/net/sctp/sysctl.c
>>>>>> +++ b/net/sctp/sysctl.c
>>>>>> @@ -40,8 +40,8 @@
>>>>>>  #include <linux/sysctl.h>
>>>>>>  
>>>>>>  static int zero = 0;
>>>>>> -static int one = 1;
>>>>>> -static int timer_max = 86400000; /* ms in one day */
>>>>>> +static int one = SCTP_ONE;
>>>>>> +static int timer_max = SCTP_TIMER_MAX;
>>>>>>  static int int_max = INT_MAX;
>>>>>>  static int sack_timer_min = 1;
>>>>>>  static int sack_timer_max = 500;
>>>>>> @@ -61,6 +61,13 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>>>>>>  				void __user *buffer, size_t *lenp,
>>>>>>  
>>>>>>  				loff_t *ppos);
>>>>>> +static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
>>>>>> +				void __user *buffer, size_t *lenp,
>>>>>> +				loff_t *ppos);
>>>>>> +static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
>>>>>> +				void __user *buffer, size_t *lenp,
>>>>>> +				loff_t *ppos);
>>>>>> +
>>>>>>  static struct ctl_table sctp_table[] = {
>>>>>>  	{
>>>>>>  		.procname	= "sctp_mem",
>>>>>> @@ -102,17 +109,17 @@ static struct ctl_table sctp_net_table[] = {
>>>>>>  		.data		= &init_net.sctp.rto_min,
>>>>>>  		.maxlen		= sizeof(unsigned int),
>>>>>>  		.mode		= 0644,
>>>>>> -		.proc_handler	= proc_dointvec_minmax,
>>>>>> +		.proc_handler	= proc_sctp_do_rto_min,
>>>>>>  		.extra1         = &one,
>>>>>> -		.extra2         = &timer_max
>>>>>> +		.extra2         = &init_net.sctp.rto_max
>>>>>>  	},
>>>>>>  	{
>>>>>>  		.procname	= "rto_max",
>>>>>>  		.data		= &init_net.sctp.rto_max,
>>>>>>  		.maxlen		= sizeof(unsigned int),
>>>>>>  		.mode		= 0644,
>>>>>> -		.proc_handler	= proc_dointvec_minmax,
>>>>>> -		.extra1         = &one,
>>>>>> +		.proc_handler	= proc_sctp_do_rto_max,
>>>>>> +		.extra1         = &init_net.sctp.rto_min,
>>>>>>  		.extra2         = &timer_max
>>>>>>  	},
>>>>>>  	{
>>>>>> @@ -342,6 +349,60 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>>>>>>  	return ret;
>>>>>>  }
>>>>>>  
>>>>>> +static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
>>>>>> +				void __user*buffer, size_t *lenp,
>>>>>> +				loff_t *ppos)
>>>>>> +{
>>>>>> +	struct net *net = current->nsproxy->net_ns;
>>>>>> +	int new_value;
>>>>>> +	struct ctl_table tbl;
>>>>>> +	unsigned int min = *(unsigned int *) ctl->extra1;
>>>>>> +	unsigned int max = *(unsigned int *) ctl->extra2;
>>>>>> +	int ret;
>>>>>> +
>>>>>> +	memset(&tbl, 0, sizeof(struct ctl_table));
>>>>>> +	tbl.maxlen = sizeof(unsigned int);
>>>>>> +
>>>>>> +	if (write)
>>>>>> +		tbl.data = &new_value;
>>>>>> +	else
>>>>>> +		tbl.data = &net->sctp.rto_min;
>>>>>> +	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
>>>>>> +	if (write) {
>>>>>> +		if (ret || new_value > max || new_value < min)
>>>>>> +			return -EINVAL;
>>>>>> +		net->sctp.rto_min = new_value;
>>>>>> +	}
>>>>>> +	return ret;
>>>>>> +}
>>>>>> +
>>>>>> +static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
>>>>>> +				void __user*buffer, size_t *lenp,
>>>>>> +				loff_t *ppos)
>>>>>> +{
>>>>>> +	struct net *net = current->nsproxy->net_ns;
>>>>>> +	int new_value;
>>>>>> +	struct ctl_table tbl;
>>>>>> +	unsigned int min = *(unsigned int *) ctl->extra1;
>>>>>> +	unsigned int max = *(unsigned int *) ctl->extra2;
>>>>>> +	int ret;
>>>>>> +
>>>>>> +	memset(&tbl, 0, sizeof(struct ctl_table));
>>>>>> +	tbl.maxlen = sizeof(unsigned int);
>>>>>> +
>>>>>> +	if (write)
>>>>>> +		tbl.data = &new_value;
>>>>>> +	else
>>>>>> +		tbl.data = &net->sctp.rto_max;
>>>>>> +	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
>>>>>> +	if (write) {
>>>>>> +                if (ret || new_value > max || new_value < min)
>>>>>> +			return -EINVAL;
>>>>>> +		net->sctp.rto_max = new_value;
>>>>>> +	}
>>>>>> +	return ret;
>>>>>> +}
>>>>>> +
>>>>>>  int sctp_sysctl_net_register(struct net *net)
>>>>>>  {
>>>>>>  	struct ctl_table *table;
>>>>>>
>>>>>
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