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

Bob Copeland
2009-02-27T02:27:54Z

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@gnu.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@bobcopeland.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