linux-kernel - [PATCH] wlan: skb_p80211_to_ether() - payload_length is unsigned, check before subtraction

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Message-ID: <4935BF7F.4080109@gmail.com>
Date:	Wed, 03 Dec 2008 00:06:39 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Greg KH <gregkh@...e.de>, linux-wireless@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: [PATCH] wlan: skb_p80211_to_ether() - payload_length is unsigned,
 check before subtraction

payload_length is unsigned, check before subtraction

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
---
diff --git a/drivers/staging/wlan-ng/p80211conv.c b/drivers/staging/wlan-ng/p80211conv.c
index 68121b9..9dd8b77 100644
--- a/drivers/staging/wlan-ng/p80211conv.c
+++ b/drivers/staging/wlan-ng/p80211conv.c
@@ -333,11 +333,11 @@ int skb_p80211_to_ether( wlandevice_t *wlandev, UINT32 ethconv, struct sk_buff *
 		memcpy(saddr, w_hdr->a3.a2, WLAN_ETHADDR_LEN);
 	} else {
 		payload_offset = WLAN_HDR_A4_LEN;
-		payload_length -= ( WLAN_HDR_A4_LEN - WLAN_HDR_A3_LEN );
-		if (payload_length < 0 ) {
+		if (payload_length < WLAN_HDR_A4_LEN - WLAN_HDR_A3_LEN) {
 			WLAN_LOG_ERROR("A4 frame too short!\n");
 			return 1;
 		}
+		payload_length -= (WLAN_HDR_A4_LEN - WLAN_HDR_A3_LEN);
 		memcpy(daddr, w_hdr->a4.a3, WLAN_ETHADDR_LEN);
 		memcpy(saddr, w_hdr->a4.a4, WLAN_ETHADDR_LEN);
 	}

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