linux-kernel - Re: [ath5k-devel] [PATCH 1/1] ath5k: fix hw rate index condition

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Date:	Thu, 26 Feb 2009 21:27:04 -0500
From:	Bob Copeland <me@...copeland.com>
To:	Jiri Slaby <jirislaby@...il.com>, proski@....org
Cc:	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	"John W. Linville" <linville@...driver.com>,
	ath5k-devel@...ema.h4ckr.net
Subject: Re: [ath5k-devel] [PATCH 1/1] ath5k: fix hw rate index condition

On Fri, Feb 27, 2009 at 12:32:55AM +0100, Jiri Slaby wrote:
> On 27.2.2009 00:28, Bob Copeland wrote:
>> hw_to_driver_rix() returns sc->rate_idx[x][y] as an int, and that
>> array is initialized to (u8)-1 for invalid rates.  So, it can
>> return 255 if the hardware rate index (y) is bad, then the check
>> "rxs.rate_idx>= 0" would always be true, right?  If it's not a
>> real bug yet, it likely will be one day :)
>
> Ah, yes, it really is a bug(tm), care to post a fix?

Actually, I remembered in the dark recesses of my moldering brain 
that someone had a lost patch for this a while ago, so I searched
the archives.  Pavel, ok to add your s-o-b?

From: Pavel Roskin <proski@....org>
Subject: [PATCH] ath5k: use signed elements for rate index table

A lookup table is used to convert from hardware rate indexes back
to driver-based rate indexes.  For unknown hardware rates, we
initialize these values to -1, but since the array elements are of
type u8, they will be in the range 0-255.  This can cause array
overruns because subsequent sanity checks only check for negative
values.

Signed-off-by: Bob Copeland <me@...copeland.com>
---
 drivers/net/wireless/ath5k/base.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/wireless/ath5k/base.h b/drivers/net/wireless/ath5k/base.h
index 20e0d14..8229561 100644
--- a/drivers/net/wireless/ath5k/base.h
+++ b/drivers/net/wireless/ath5k/base.h
@@ -112,7 +112,7 @@ struct ath5k_softc {
 	struct ieee80211_supported_band sbands[IEEE80211_NUM_BANDS];
 	struct ieee80211_channel channels[ATH_CHAN_MAX];
 	struct ieee80211_rate	rates[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
-	u8			rate_idx[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
+	s8			rate_idx[IEEE80211_NUM_BANDS][AR5K_MAX_RATES];
 	enum nl80211_iftype	opmode;
 	struct ath5k_hw		*ah;		/* Atheros HW */
 
-- 
1.5.4.1


-- 
Bob Copeland %% www.bobcopeland.com

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