linux-kernel - [patch] zd1211rw: fix potential array underflow

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Date:	Sat, 27 Feb 2010 09:12:34 +0300
From:	Dan Carpenter <error27@...il.com>
To:	Daniel Drake <dsd@...too.org>
Cc:	Ulrich Kunitz <kune@...ne-taler.de>,
	"John W. Linville" <linville@...driver.com>,
	Johannes Berg <johannes@...solutions.net>,
	"Luis R. Rodriguez" <lrodriguez@...eros.com>,
	André Goddard Rosa <andre.goddard@...il.com>,
	Benoit PAPILLAULT <benoit.papillault@...e.fr>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [patch] zd1211rw: fix potential array underflow

The first chunk fixes a debugging assert to print a warning about array underflows.
The second chunk corrects a potential array underflow.  I also removed an assert
in the second chunk because it can no longer happen.

Signed-off-by: Dan Carpenter <error27@...il.com>
---
This was found by a static check and compile tested only.  Please review carefully.

diff --git a/drivers/net/wireless/zd1211rw/zd_mac.c b/drivers/net/wireless/zd1211rw/zd_mac.c
index f14deb0..ead2f2c 100644
--- a/drivers/net/wireless/zd1211rw/zd_mac.c
+++ b/drivers/net/wireless/zd1211rw/zd_mac.c
@@ -350,7 +350,7 @@ static void zd_mac_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 	first_idx = info->status.rates[0].idx;
 	ZD_ASSERT(0<=first_idx && first_idx<ARRAY_SIZE(zd_retry_rates));
 	retries = &zd_retry_rates[first_idx];
-	ZD_ASSERT(0<=retry && retry<=retries->count);
+	ZD_ASSERT(1 <= retry && retry <= retries->count);
 
 	info->status.rates[0].idx = retries->rate[0];
 	info->status.rates[0].count = 1; // (retry > 1 ? 2 : 1);
@@ -360,7 +360,7 @@ static void zd_mac_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb,
 		info->status.rates[i].count = 1; // ((i==retry-1) && success ? 1:2);
 	}
 	for (; i<IEEE80211_TX_MAX_RATES && i<retry; i++) {
-		info->status.rates[i].idx = retries->rate[retry-1];
+		info->status.rates[i].idx = retries->rate[retry - 1];
 		info->status.rates[i].count = 1; // (success ? 1:2);
 	}
 	if (i<IEEE80211_TX_MAX_RATES)
@@ -424,12 +424,10 @@ void zd_mac_tx_failed(struct urb *urb)
 		first_idx = info->status.rates[0].idx;
 		ZD_ASSERT(0<=first_idx && first_idx<ARRAY_SIZE(zd_retry_rates));
 		retries = &zd_retry_rates[first_idx];
-		if (retry < 0 || retry > retries->count) {
+		if (retry <= 0 || retry > retries->count)
 			continue;
-		}
 
-		ZD_ASSERT(0<=retry && retry<=retries->count);
-		final_idx = retries->rate[retry-1];
+		final_idx = retries->rate[retry - 1];
 		final_rate = zd_rates[final_idx].hw_value;
 
 		if (final_rate != tx_status->rate) {
--
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