[PATCH] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

[PATCH] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

[Arend van Spriel]

User-space can choose to omit NL80211_ATTR_SSID and only provide raw
IE TLV data. When doing so it can provide SSID IE with length exceeding
the allowed size. The driver further processes this IE copying it
into a local variable without checking the length. Hence stack can be
corrupted and used as exploit.

Cc: stable@vger.kernel.org # v4.7
Reported-by: Daxing Guo <freener.gdx@gmail.com>
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
index 5db56a7..b8aec5e5 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
@@ -4527,7 +4527,7 @@ brcmf_cfg80211_start_ap(struct wiphy *wiphy, struct net_device *ndev,
 				(u8 *)&settings->beacon.head[ie_offset],
 				settings->beacon.head_len - ie_offset,
 				WLAN_EID_SSID);
-		if (!ssid_ie)
+		if (!ssid_ie || ssid_ie->len > IEEE80211_MAX_SSID_LEN)
 			return -EINVAL;
 
 		memcpy(ssid_le.SSID, ssid_ie->data, ssid_ie->len);
-- 
1.9.1

Re: [PATCH] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

[Arend Van Spriel]

On 5-9-2016 11:45, Arend van Spriel wrote:
> User-space can choose to omit NL80211_ATTR_SSID and only provide raw
> IE TLV data. When doing so it can provide SSID IE with length exceeding
> the allowed size. The driver further processes this IE copying it
> into a local variable without checking the length. Hence stack can be
> corrupted and used as exploit.

This patch is intended for wireless-drivers repository, ie. for v4.8.

Regards,
Arend

> Cc: stable@vger.kernel.org # v4.7
> Reported-by: Daxing Guo <freener.gdx@gmail.com>
> Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
> Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
> Reviewed-by: Franky Lin <franky.lin@broadcom.com>
> Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
> ---
>  drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index 5db56a7..b8aec5e5 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> @@ -4527,7 +4527,7 @@ brcmf_cfg80211_start_ap(struct wiphy *wiphy, struct net_device *ndev,
>  				(u8 *)&settings->beacon.head[ie_offset],
>  				settings->beacon.head_len - ie_offset,
>  				WLAN_EID_SSID);
> -		if (!ssid_ie)
> +		if (!ssid_ie || ssid_ie->len > IEEE80211_MAX_SSID_LEN)
>  			return -EINVAL;
>  
>  		memcpy(ssid_le.SSID, ssid_ie->data, ssid_ie->len);
> 

Re: brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

[Kalle Valo]

Arend Van Spriel <arend.vanspriel@broadcom.com> wrote:
> User-space can choose to omit NL80211_ATTR_SSID and only provide raw
> IE TLV data. When doing so it can provide SSID IE with length exceeding
> the allowed size. The driver further processes this IE copying it
> into a local variable without checking the length. Hence stack can be
> corrupted and used as exploit.
> 
> Cc: stable@vger.kernel.org # v4.7
> Reported-by: Daxing Guo <freener.gdx@gmail.com>
> Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
> Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
> Reviewed-by: Franky Lin <franky.lin@broadcom.com>
> Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>

Thanks, 1 patch applied to wireless-drivers.git:

ded89912156b brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

-- 
Sent by pwcli
https://patchwork.kernel.org/patch/9313305/