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From: John W. Linville <linville@tuxdriver.com>
Date: Tue, 2 Oct 2007 04:03:54 +0000 (-0700)
Subject: [IEEE80211]: avoid integer underflow for runt rx frames
X-Git-Tag: kvm-47~34^2~42^2
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Favi%2Fkvm.git;a=commitdiff_plain;h=04045f98e0457aba7d4e6736f37eed189c48a5f7
[IEEE80211]: avoid integer underflow for runt rx frames
Reported by Chris Evans <scarybeasts@gmail.com>:
> 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 <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
diff --git a/net/ieee80211/ieee80211_rx.c b/net/ieee80211/ieee80211_rx.c
index f2de2e4..6284c99 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
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