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

[Arend van Spriel <arend.vanspriel@broadcom.com>]

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?

Regards,
Arend

>   	frame = memdup_user(buf, len);
>   	if (IS_ERR(frame))
>   		return PTR_ERR(frame);
>