Subject: Re: [PATCH] rtnetlink: Mask the rta_type when range checking

From: Vlad Yasevich <[email-masked]>
Date: Wed, 13 Mar 2013 11:41:46 -0400

On 03/13/2013 11:36 AM, Stephen Hemminger wrote:
> On Wed, 13 Mar 2013 10:18:58 -0400
> Vlad Yasevich <[email-masked]> wrote:
>
>> Range/validity checks on rta_type in rtnetlink_rcv_msg() do
>> not account for flags that may be set.  This causes the function
>> to return -EINVAL when flags are set on the type (for example
>> NLA_F_NESTED).
>>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
>> ---
>>   net/core/rtnetlink.c |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index 1868625..dc5edf1 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -2538,7 +2538,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>   		struct rtattr *attr = (void *)nlh + NLMSG_ALIGN(min_len);
>>
>>   		while (RTA_OK(attr, attrlen)) {
>> -			unsigned int flavor = attr->rta_type;
>> +			unsigned int flavor = attr->rta_type & NLA_TYPE_MASK;
>>   			if (flavor) {
>>   				if (flavor > rta_max[sz_idx])
>>   					return -EINVAL;
>
> No. This is effectively an ABI change. It adds nothing.
>

It makes nested IFLA_PROTINFO work that the bridge code expects. 
Without this change, sending a nested IFLA_PROTINFO causes a EIVNAL
return.

-vlad

> The NLA_F_NESTED attribute wasn't in the first generation version of netlink
> (before my time with Linux). It doesn't make sense to all of sudden start
> accepting it on requests. Also, then you would expect the query to set
> the NESTED flag as well, and that would be another ABI change.
>