[PATCH 5.4 32/38] wifi: cfg80211: ensure length byte is present before access

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Johannes Berg <johannes.berg@intel.com>

commit 567e14e39e8f8c6997a1378bc3be615afca86063 upstream.

When iterating the elements here, ensure the length byte is
present before checking it to see if the entire element will
fit into the buffer.

Longer term, we should rewrite this code using the type-safe
element iteration macros that check all of this.

Fixes: 0b8fb8235be8 ("cfg80211: Parsing of Multiple BSSID information in scanning")
Reported-by: Soenke Huster <shuster@seemoo.tu-darmstadt.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/wireless/scan.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -265,7 +265,8 @@ static size_t cfg80211_gen_new_ie(const
 	tmp_old = cfg80211_find_ie(WLAN_EID_SSID, ie, ielen);
 	tmp_old = (tmp_old) ? tmp_old + tmp_old[1] + 2 : ie;
 
-	while (tmp_old + tmp_old[1] + 2 - ie <= ielen) {
+	while (tmp_old + 2 - ie <= ielen &&
+	       tmp_old + tmp_old[1] + 2 - ie <= ielen) {
 		if (tmp_old[0] == 0) {
 			tmp_old++;
 			continue;
@@ -325,7 +326,8 @@ static size_t cfg80211_gen_new_ie(const
 	 * copied to new ie, skip ssid, capability, bssid-index ie
 	 */
 	tmp_new = sub_copy;
-	while (tmp_new + tmp_new[1] + 2 - sub_copy <= subie_len) {
+	while (tmp_new + 2 - sub_copy <= subie_len &&
+	       tmp_new + tmp_new[1] + 2 - sub_copy <= subie_len) {
 		if (!(tmp_new[0] == WLAN_EID_NON_TX_BSSID_CAP ||
 		      tmp_new[0] == WLAN_EID_SSID)) {
 			memcpy(pos, tmp_new, tmp_new[1] + 2);