Re: [PATCH] staging: rtl8723bs: fix frame length underflow in OnAuthClient

[Dan Carpenter <error27@gmail.com>]

On Tue, Apr 14, 2026 at 12:08:04PM +0200, Alexandru Hossu wrote:
> If pkt_len is less than WLAN_HDR_A3_LEN + offset + 6, the reads of
> the seq and status fields go beyond the frame buffer. Additionally,
> when pkt_len < WLAN_HDR_A3_LEN + _AUTH_IE_OFFSET_ (30 bytes), the
> subtraction passed to rtw_get_ie() wraps around since pkt_len is
> unsigned, causing rtw_get_ie() to scan well past the end of the buffer.
> 
> Add a minimum length check after computing offset to reject frames
> that are too short before any fixed field access.
> 
> Reported-by: Dan Carpenter <error27@gmail.com>
> Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexandru Hossu <hossu.alexandru@gmail.com>
> ---
>  drivers/staging/rtl8723bs/core/rtw_mlme_ext.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> index 90f27665667a..6b0ac54ad3d4 100644
> --- a/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> +++ b/drivers/staging/rtl8723bs/core/rtw_mlme_ext.c
> @@ -869,6 +869,9 @@ unsigned int OnAuthClient(struct adapter *padapter, union recv_frame *precv_fram
>  
>  	offset = (GetPrivacy(pframe)) ? 4 : 0;
                             ^^^^^^
Do we know for sure that this is within bounds?  And there is earlier
code which pokes in pframe as well.  This code is quite complicated.

I looked at how to do bounds checking but it all seems pretty
complicated to me and I haven't investigated this enough to know the
right answers.

regards,
dan carpenter

>  
> +	if (pkt_len < WLAN_HDR_A3_LEN + offset + 6)
> +		goto authclnt_fail;
> +
>  	seq	= le16_to_cpu(*(__le16 *)((SIZE_PTR)pframe + WLAN_HDR_A3_LEN + offset + 2));
>  	status	= le16_to_cpu(*(__le16 *)((SIZE_PTR)pframe + WLAN_HDR_A3_LEN + offset + 4));
>  
> -- 
> 2.53.0