linux-kernel - [PATCH 3.10 246/319] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start

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Message-Id: <1486322541-8206-147-git-send-email-w@1wt.eu>
Date:   Sun,  5 Feb 2017 20:21:08 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Kalle Valo <kvalo@...eaurora.org>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 246/319] brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

From: Arend Van Spriel <arend.vanspriel@...adcom.com>

commit ded89912156b1a47d940a0c954c43afbabd0c42c upstream.

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.

Reported-by: Daxing Guo <freener.gdx@...il.com>
Reviewed-by: Hante Meuleman <hante.meuleman@...adcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>
Reviewed-by: Franky Lin <franky.lin@...adcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@...adcom.com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
index 301e572..2c52430 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
@@ -3726,7 +3726,7 @@ 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);
-- 
2.8.0.rc2.1.gbe9624a