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(+)

diff --git a/src/ap/wmm.c b/src/ap/wmm.c

index 6d4177c..314e244 100644

--- a/src/ap/wmm.c

+++ b/src/ap/wmm.c

@@ -274,6 +274,9 @@ void hostapd_wmm_action(struct hostapd_data *hapd,

 		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,

-- 

1.9.1