[PATCH 4.9 34/60] mac80211: Fix adding of mesh vendor IEs

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thorsten Horstmann <thorsten@xxxxxxxxxxx>

commit da7061c82e4a1bc6a5e134ef362c86261906c860 upstream.

The function ieee80211_ie_split_vendor doesn't return 0 on errors. Instead
it returns any offset < ielen when WLAN_EID_VENDOR_SPECIFIC is found. The
return value in mesh_add_vendor_ies must therefore be checked against
ifmsh->ie_len and not 0. Otherwise all ifmsh->ie starting with
WLAN_EID_VENDOR_SPECIFIC will be rejected.

Fixes: 082ebb0c258d ("mac80211: fix mesh beacon format")
Signed-off-by: Thorsten Horstmann <thorsten@xxxxxxxxxxx>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@xxxxxxxxxxxxxxxxx>
Signed-off-by: Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx>
[sven@xxxxxxxxxxxxx: Add commit message]
Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/mac80211/mesh.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -339,7 +339,7 @@ int mesh_add_vendor_ies(struct ieee80211
 	/* fast-forward to vendor IEs */
 	offset = ieee80211_ie_split_vendor(ifmsh->ie, ifmsh->ie_len, 0);
 
-	if (offset) {
+	if (offset < ifmsh->ie_len) {
 		len = ifmsh->ie_len - offset;
 		data = ifmsh->ie + offset;
 		if (skb_tailroom(skb) < len)