brcmfmac: avoid potential stack overflow in brcmf_cfg80211_start_ap()

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@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>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
index d8fa276e368b4fc038b62a941191b3d25393b8f6..9e6502a9648cac225051b81777ee45118f9a1084 100644 (file)
--- a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
@@ -3822,7 +3822,7 @@ 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);