Subject: Re: [PATCH v3] sctp: check the rto_min and rto_max

From: Vlad Yasevich <[email-masked]>
Date: Tue, 03 Dec 2013 07:39:47 -0500

On 12/03/2013 01:28 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]>
> ---
>  net/sctp/socket.c |  5 +++++
>  net/sctp/sysctl.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 56 insertions(+), 7 deletions(-)
> 
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 72046b9..2e1af1b 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 < 1 ||
> +	    rtoinfo.srto_max > 86400000 ||
> +	    rtoinfo.srto_max < rtoinfo.srto_min)
> +		return -EINVAL;
> +
>  	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..525b06d 100644
> --- a/net/sctp/sysctl.c
> +++ b/net/sctp/sysctl.c
> @@ -59,8 +59,16 @@ extern int sysctl_sctp_wmem[3];
>  static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>  				int write,
>  				void __user *buffer, size_t *lenp,
> -
>  				loff_t *ppos);
> +static int proc_sctp_check_rtomin(struct ctl_table *ctl,
> +				int write,
> +				void __user *buffer, size_t *lenp,
> +				loff_t *ppos);
> +static int proc_sctp_check_rtomax(struct ctl_table *ctl,
> +				int write,
> +				void __user *buffer, size_t *lenp,
> +				loff_t *ppos);
> +
>  static struct ctl_table sctp_table[] = {
>  	{
>  		.procname	= "sctp_mem",
> @@ -102,18 +110,14 @@ static struct ctl_table sctp_net_table[] = {
>  		.data		= &init_net.sctp.rto_min,
>  		.maxlen		= sizeof(unsigned int),
>  		.mode		= 0644,
> -		.proc_handler	= proc_dointvec_minmax,
> -		.extra1         = &one,
> -		.extra2         = &timer_max
> +		.proc_handler	= proc_sctp_check_rtomin,
>  	},
>  	{
>  		.procname	= "rto_max",
>  		.data		= &init_net.sctp.rto_max,
>  		.maxlen		= sizeof(unsigned int),
>  		.mode		= 0644,
> -		.proc_handler	= proc_dointvec_minmax,
> -		.extra1         = &one,
> -		.extra2         = &timer_max
> +		.proc_handler	= proc_sctp_check_rtomax,
>  	},
>  	{
>  		.procname	= "rto_alpha_exp_divisor",
> @@ -342,6 +346,46 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl,
>  	return ret;
>  }
>  
> +static int proc_sctp_check_rtomin(struct ctl_table *ctl,
> +				int write,
> +				void __user *buffer, size_t *lenp,
> +				loff_t *ppos)
> +{
> +	int old_value = *(int *) ctl->data;
> +	int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
> +
> +	if (write) {
> +		int new_value = *(int *) ctl->data;
> +		if (ret || new_value < one || new_value > init_net.sctp.rto_max) {
> +			init_net.sctp.rto_min = old_value;
> +			return -EINVAL;
> +		}
> +		init_net.sctp.rto_min = new_value;
> +	}
> +
> +	return ret;
> +}
> +
> +static int proc_sctp_check_rtomax(struct ctl_table *ctl,
> +				int write,
> +				void __user*buffer, size_t *lenp,
> +				loff_t *ppos)
> +{
> +	int old_value = *(int *) ctl->data;
> +	int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
> +
> +	if (write) {
> +		int new_value = *(int *) ctl->data;
> +		if (ret || new_value > timer_max || new_value < init_net.sctp.rto_min) {
> +			init_net.sctp.rto_max = old_value;
> +			return -EINVAL;
> +		}
> +		init_net.sctp.rto_max = new_value;
> +	}
> +
> +	return ret;
> +}
> +

You can't used init_net directly.  You have to use .data as the target
of assignment and .extra1 and .extra2 as the min and max boundries.
Otherwise, this has the same problem as before where assignments for
created namespace try to change the values in the initial namespace.

-vlad
>  int sctp_sysctl_net_register(struct net *net)
>  {
>  	struct ctl_table *table;
>