hostapd: fix remote denial of service vulnerability in WMM action frame parsing

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 45619

package/network/services/hostapd/patches/002-AP-WMM-Fix-integer-underflow-in-WMM-Action-frame-par.patch

@@ -0,0 +1,36 @@
+From ef566a4d4f74022e1fdb0a2addfe81e6de9f4aae Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <j@w1.fi>
+Date: Wed, 29 Apr 2015 02:21:53 +0300
+Subject: [PATCH] AP WMM: Fix integer underflow in WMM Action frame parser
+
+The length of the WMM Action frame was not properly validated and the
+length of the information elements (int left) could end up being
+negative. This would result in reading significantly past the stack
+buffer while parsing the IEs in ieee802_11_parse_elems() and while doing
+so, resulting in segmentation fault.
+
+This can result in an invalid frame being used for a denial of service
+attack (hostapd process killed) against an AP with a driver that uses
+hostapd for management frame processing (e.g., all mac80211-based
+drivers).
+
+Thanks to Kostya Kortchinsky of Google security team for discovering and
+reporting this issue.
+
+Signed-off-by: Jouni Malinen <j@w1.fi>
+---
+ src/ap/wmm.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/src/ap/wmm.c
++++ b/src/ap/wmm.c
+@@ -274,6 +274,9 @@ void hostapd_wmm_action(struct hostapd_d
+ 		return;
+ 	}
+ 
++	if (left < 0)
++		return; /* not a valid WMM Action frame */
++
+ 	/* extract the tspec info element */
+ 	if (ieee802_11_parse_elems(pos, left, &elems, 1) == ParseFailed) {
+ 		hostapd_logger(hapd, mgmt->sa, HOSTAPD_MODULE_IEEE80211,