[net-next] netlink: add missing length check of rtnl msg

When the legacy array rtm_min still exists, the length check within these 
functions is covered by rtm_min[RTM_NEWTFILTER], rtm_min[RTM_NEWQDISC] 
and rtm_min[RTM_NEWTCLASS].

But after Thomas Graf removed rtm_min several days ago, these checks are 
missing. 

Other doit functions should be OK.

Signed-off-by: Hong Zhiguo <honkiko@gmail.com>
---
 net/sched/cls_api.c |    4 ++++
 net/sched/sch_api.c |   22 ++++++++++++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

From: Hong Zhiguo <honkiko@gmail.com>
Date: Tue, 26 Mar 2013 01:22:23 +0800

> When the legacy array rtm_min still exists, the length check within these 
> functions is covered by rtm_min[RTM_NEWTFILTER], rtm_min[RTM_NEWQDISC] 
> and rtm_min[RTM_NEWTCLASS].
> 
> But after Thomas Graf removed rtm_min several days ago, these checks are 
> missing. 
> 
> Other doit functions should be OK.
> 
> Signed-off-by: Hong Zhiguo <honkiko@gmail.com>

This looks good, Thomas please review.
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On 03/26/13 at 01:22am, Hong Zhiguo wrote:
>  	protocol = TC_H_MIN(t->tcm_info);
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 0bbce22..b30a988 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -977,7 +977,7 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n)
>  	struct tcmsg *tcm = nlmsg_data(n);
>  	struct nlattr *tca[TCA_MAX + 1];
>  	struct net_device *dev;
> -	u32 clid = tcm->tcm_parent;
> +	u32 clid;
>  	struct Qdisc *q = NULL;
>  	struct Qdisc *p = NULL;
>  	int err;
> @@ -985,6 +985,9 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n)
>  	if ((n->nlmsg_type != RTM_GETQDISC) && !capable(CAP_NET_ADMIN))
>  		return -EPERM;
>  
> +	if (nlmsg_len(n) < sizeof(*tcm))
> +		return -EINVAL;
> +
>  	dev = __dev_get_by_index(net, tcm->tcm_ifindex);
>  	if (!dev)
>  		return -ENODEV;

What do you think about moving the nlmsg_parse() call from below here
to before __dev_get_by_index()? It also verifies the header length and
it's how other netlink code verifies the message type specific header
as well.

>  	if (err < 0)
> @@ -1051,6 +1055,9 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n)
>  	if (!capable(CAP_NET_ADMIN))
>  		return -EPERM;
>  
> +	if (nlmsg_len(n) < sizeof(*tcm))
> +		return -EINVAL;
> +

Same here.

>  replay:
>  	/* Reinit, just in case something touches this. */
>  	tcm = nlmsg_data(n);
> @@ -1382,14 +1389,17 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n)
>  	const struct Qdisc_class_ops *cops;
>  	unsigned long cl = 0;
>  	unsigned long new_cl;
> -	u32 portid = tcm->tcm_parent;
> -	u32 clid = tcm->tcm_handle;
> -	u32 qid = TC_H_MAJ(clid);
> +	u32 portid;
> +	u32 clid;
> +	u32 qid;
>  	int err;
>  
>  	if ((n->nlmsg_type != RTM_GETTCLASS) && !capable(CAP_NET_ADMIN))
>  		return -EPERM;
>  
> +	if (nlmsg_len(n) < sizeof(*tcm))
> +		return -EINVAL;
> +
>  	dev = __dev_get_by_index(net, tcm->tcm_ifindex);
>  	if (!dev)
>  		return -ENODEV;

And here.
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