Re: [PATCH 2/2] staging: rtl8723bs: bound SUPP_RATES IE length in rtw_check_beacon_data

[Dan Carpenter]

On Mon, May 11, 2026 at 06:44:56PM -0700, Shayaun Nejad wrote:
> rtw_check_beacon_data() copies SUPP_RATES and EXT_SUPP_RATES IE
> payloads into a 16-byte support_rate[] buffer.
> 
> The IE lengths are used directly, so oversized rate IEs can overflow the
> stack buffer.
> 
> Clamp the supported rates copy and the combined extended supported rates
> copy to NDIS_802_11_LENGTH_RATES_EX.
> 
> Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Shayaun Nejad <snejad123@xxxxxxxxx>
> ---
>  drivers/staging/rtl8723bs/core/rtw_ap.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8723bs/core/rtw_ap.c b/drivers/staging/rtl8723bs/core/rtw_ap.c
> index 4b40124110..363ecb02b5 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_ap.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_ap.c
> @@ -873,6 +873,7 @@ int rtw_check_beacon_data(struct adapter *padapter, u8 *pbuf,  int len)
>  		       &ie_len,
>  		       (pbss_network->ie_length - _BEACON_IE_OFFSET_));
>  	if (p) {
> +		ie_len = min_t(uint, ie_len, NDIS_802_11_LENGTH_RATES_EX);

These days we would use umin()

>  		memcpy(support_rate, p + 2, ie_len);
>  		support_rate_num = ie_len;

support_rate_num is set here.  We know from the min_t() that it's less
<= NDIS_802_11_LENGTH_RATES_EX.

>  	}
> @@ -882,8 +883,11 @@ int rtw_check_beacon_data(struct adapter *padapter, u8 *pbuf,  int len)
>  		       WLAN_EID_EXT_SUPP_RATES,
>  		       &ie_len,
>  		       pbss_network->ie_length - _BEACON_IE_OFFSET_);
> -	if (p)
> +	if (p && support_rate_num < NDIS_802_11_LENGTH_RATES_EX) {

We know that support_rate_num <= NDIS_802_11_LENGTH_RATES_EX.  Allowing
== NDIS_802_11_LENGTH_RATES_EX is okay because memcpy() of zero bytes is
a no-op.

> +		ie_len = min_t(uint, ie_len,
> +			       NDIS_802_11_LENGTH_RATES_EX - support_rate_num);

Use umin() here too.

Otherwise the patch is fine.

regards,
dan carpenter

>  		memcpy(support_rate + support_rate_num, p + 2, ie_len);
> +	}
>  
>  	network_type = rtw_check_network_type(support_rate, channel);
>  
> -- 
> 2.43.0
>