From 04045f98e0457aba7d4e6736f37eed189c48a5f7 Mon Sep 17 00:00:00 2001 From: "John W. Linville" Date: Mon, 1 Oct 2007 21:03:54 -0700 Subject: [PATCH] [IEEE80211]: avoid integer underflow for runt rx frames Reported by Chris Evans : > The summary is that an evil 80211 frame can crash out a victim's > machine. It only applies to drivers using the 80211 wireless code, and > only then to certain drivers (and even then depends on a card's > firmware not dropping a dubious packet). I must confess I'm not > keeping track of Linux wireless support, and the different protocol > stacks etc. > > Details are as follows: > > ieee80211_rx() does not explicitly check that "skb->len >= hdrlen". > There are other skb->len checks, but not enough to prevent a subtle > off-by-two error if the frame has the IEEE80211_STYPE_QOS_DATA flag > set. > > This leads to integer underflow and crash here: > > if (frag != 0) > flen -= hdrlen; > > (flen is subsequently used as a memcpy length parameter). How about this? Signed-off-by: John W. Linville Signed-off-by: David S. Miller --- net/ieee80211/ieee80211_rx.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ieee80211/ieee80211_rx.c b/net/ieee80211/ieee80211_rx.c index f2de2e48b02..6284c99b456 100644 --- a/net/ieee80211/ieee80211_rx.c +++ b/net/ieee80211/ieee80211_rx.c @@ -366,6 +366,12 @@ int ieee80211_rx(struct ieee80211_device *ieee, struct sk_buff *skb, frag = WLAN_GET_SEQ_FRAG(sc); hdrlen = ieee80211_get_hdrlen(fc); + if (skb->len < hdrlen) { + printk(KERN_INFO "%s: invalid SKB length %d\n", + dev->name, skb->len); + goto rx_dropped; + } + /* Put this code here so that we avoid duplicating it in all * Rx paths. - Jean II */ #ifdef CONFIG_WIRELESS_EXT -- 2.20.1