Re: [PATCH v4 01/10] wil6210: protect against invalid length of tx management frame

[Lior David <liord@codeaurora.org>]

On 8/9/2017 11:02 AM, Arend van Spriel wrote:
> On 8/3/2017 9:08 PM, Maya Erez wrote:
>> From: Hamad Kadmany <qca_hkadmany@qca.qualcomm.com>
>>
>> Validate buffer length has the minimum needed size
>> when sending management frame to protect against
>> possible buffer overrun.
> 
> I noticed this is already applied, but I saw this subject text which has similar
> sound to a recent patch in our driver so I it made me curious...
> 
>> Signed-off-by: Hamad Kadmany <qca_hkadmany@qca.qualcomm.com>
>> Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
>> Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
>> ---
>>   drivers/net/wireless/ath/wil6210/cfg80211.c | 3 +++
>>   drivers/net/wireless/ath/wil6210/debugfs.c  | 3 +++
>>   2 files changed, 6 insertions(+)
>>
>> diff --git a/drivers/net/wireless/ath/wil6210/cfg80211.c
>> b/drivers/net/wireless/ath/wil6210/cfg80211.c
>> index 0b5383a..77af749 100644
>> --- a/drivers/net/wireless/ath/wil6210/cfg80211.c
>> +++ b/drivers/net/wireless/ath/wil6210/cfg80211.c
>> @@ -884,6 +884,9 @@ int wil_cfg80211_mgmt_tx(struct wiphy *wiphy, struct
>> wireless_dev *wdev,
>>       wil_hex_dump_misc("mgmt tx frame ", DUMP_PREFIX_OFFSET, 16, 1, buf,
>>                 len, true);
>>
>> +    if (len < sizeof(struct ieee80211_hdr_3addr))
>> +        return -EINVAL;
> 
> A similar check is already in net/wireless/cfg80211_mlme_mgmt_tx() which calls
> this function:
> 
>     if (params->len < 24 + 1)
>         return -EINVAL;
> 
> So it only makes sense if this is called from some other call site....
> 
>>       cmd = kmalloc(sizeof(*cmd) + len, GFP_KERNEL);
>>       if (!cmd) {
>>           rc = -ENOMEM;
>> diff --git a/drivers/net/wireless/ath/wil6210/debugfs.c
>> b/drivers/net/wireless/ath/wil6210/debugfs.c
>> index f82506d..a2b5d59 100644
>> --- a/drivers/net/wireless/ath/wil6210/debugfs.c
>> +++ b/drivers/net/wireless/ath/wil6210/debugfs.c
>> @@ -801,6 +801,9 @@ static ssize_t wil_write_file_txmgmt(struct file *file,
>> const char __user *buf,
>>       int rc;
>>       void *frame;
>>
>> +    if (!len)
>> +        return -EINVAL;
>> +
> 
> ... which is in this function. Now I wonder why you would need this method in
> the first place. Why not stick with using the nl80211 NL80211_CMD_FRAME api?
> 
Using NL80211_CMD_FRAME reaches cfg80211_mlme_mgmt_tx which performs validity
checks such as:
- Fail to send frame types not supported by the driver
- Some strict checks for non-public action frames.
The debugfs file provides a convenient and simple way to send any type of
management frames for debugging and testing. For example, we use it with some
testing scripts, basically turning a station into a "packet injector" and
sending frames into the air for simulating various scenarios.

Thanks,
Lior