RE: [PATCH] rtlwifi: Fix potential overflow on P2P code

[Pkshih <pkshih@realtek.com>]

> -----Original Message-----
> From: linux-wireless-owner@vger.kernel.org [mailto:linux-wireless-owner@vger.kernel.org] On Behalf
> Of Laura Abbott
> Sent: Thursday, October 17, 2019 4:57 AM
> To: Pkshih; Kalle Valo
> Cc: Laura Abbott; David S. Miller; linux-wireless@vger.kernel.org; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org; Nicolas Waisman
> Subject: [PATCH] rtlwifi: Fix potential overflow on P2P code
> 
> Nicolas Waisman noticed that even though noa_len is checked for
> a compatible length it's still possible to overrun the buffers
> of p2pinfo since there's no check on the upper bound of noa_num.
> Bounds check noa_num against P2P_MAX_NOA_NUM.
> 
> Reported-by: Nicolas Waisman <nico@semmle.com>
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> Compile tested only as this was reported to the security list.
> ---
>  drivers/net/wireless/realtek/rtlwifi/ps.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/ps.c b/drivers/net/wireless/realtek/rtlwifi/ps.c
> index 70f04c2f5b17..c5cff598383d 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/ps.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/ps.c
> @@ -754,6 +754,13 @@ static void rtl_p2p_noa_ie(struct ieee80211_hw *hw, void *data,
>  				return;
>  			} else {
>  				noa_num = (noa_len - 2) / 13;
> +				if (noa_num > P2P_MAX_NOA_NUM) {
> +					RT_TRACE(rtlpriv, COMP_INIT, DBG_LOUD,
> +						 "P2P notice of absence: invalid noa_num.%d\n",
> +						 noa_num);
> +					return;

As the discussion at <security@kernel.org>, I think it'd be better to use
the min between noa_num and P2P_MAX_NOA_NUM, and fall through the code instead
of return. Because ignore all NoA isn't better than apply two of them.


> +				}
> +
>  			}
>  			noa_index = ie[3];
>  			if (rtlpriv->psc.p2p_ps_info.p2p_ps_mode ==
> @@ -848,6 +855,13 @@ static void rtl_p2p_action_ie(struct ieee80211_hw *hw, void *data,
>  				return;
>  			} else {
>  				noa_num = (noa_len - 2) / 13;
> +				if (noa_num > P2P_MAX_NOA_NUM) {
> +					RT_TRACE(rtlpriv, COMP_FW, DBG_LOUD,
> +						 "P2P notice of absence: invalid noa_len.%d\n",
> +						 noa_len);
> +					return;
> +
> +				}
>  			}
>  			noa_index = ie[3];
>  			if (rtlpriv->psc.p2p_ps_info.p2p_ps_mode ==
> --
> 2.21.0