Re: [PATCH] cfg80211: Validate legacy rateset.

[Bala Shanmugam <bkamatch@qca.qualcomm.com>]

On 04/17/2012 07:29 PM, Johannes Berg wrote:
> On 4/17/2012 1:07 AM, Bala Shanmugam wrote:
>> On 04/16/2012 11:01 PM, Johannes Berg wrote:
>>> On 4/12/2012 11:22 PM, Bala Shanmugam wrote:
>>>> Legacy rates are not validated while configuring
>>>> tx rateset using iw. So below cmd is accepted by nl80211.
>>>> sudo iw wlan2 set bitrates legacy-2.4 3
>>>>
>>>> Validate legacy rates and return
>>>> error while configuring improper rates.
>>>>
>>>> Signed-off-by: Bala Shanmugam<bkamatch@qca.qualcomm.com>
>>>> ---
>>>> net/wireless/nl80211.c | 2 ++
>>>> 1 files changed, 2 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
>>>> index e49da27..cc7bef7 100644
>>>> --- a/net/wireless/nl80211.c
>>>> +++ b/net/wireless/nl80211.c
>>>> @@ -5540,6 +5540,8 @@ static int nl80211_set_tx_bitrate_mask(struct
>>>> sk_buff *skb,
>>>> sband,
>>>> nla_data(tb[NL80211_TXRATE_LEGACY]),
>>>> nla_len(tb[NL80211_TXRATE_LEGACY]));
>>>> + if (mask.control[band].legacy == 0)
>>>> + return -EINVAL;
>>>
>>> I don't think this is right since it would also reject an
>>> intentionally empty set.
>
>> This check comes into picture only when legacy rates are configured.
>> For intentionally empty set "if (tb[NL80211_TXRATE_LEGACY])" condition
>> will fail and control will not come here. I tested the same.
>> With this patch
>> "sudo iw wlan0 set bitrates mcs-5 6" executes without any error message.
>
> However, that means "don't change legacy settings", not "empty legacy 
> rateset".
>
> johannes
Good catch.
I didn't think of below configuration which is to specify empty legacy 
rateset for 2.4 band.
sudo iw wlan0 set bitrates legacy-2.4
Correct me if I am wrong.

Anyway we need to reject invalid legacy rates and below additional check 
will allow empty rateset
and block invalid rates
if (mask.control[band].legacy == 0 && nla_len(tb[NL80211_TXRATE_LEGACY]))
   return -EINVAL;

Will send new patch.

Regards,
Bala.