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>
Acked-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
index 571f013cebbb0d0a80f32e2351975b659d7d53d1..f2e245bc452024db6c75c3a10ea1b1c05ceb84dd 100644 (file)
--- a/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/wl_cfg80211.c
@@ -3731,7 +3731,7 @@ 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);