zd1211rw: fix potential array underflow

PATCH In review Dan Carpenter 3 participants 4 messages Feb 27, 2010

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Dan Carpenter

author

2010-02-27 06:12 UTC #0 lore raw

PATCH 1/1 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 <[email protected]>

---
This was found by a static check and compile tested only. Please review carefully.

drivers/net/wireless/zd1211rw/zd_mac.c +4 -6

index f14deb0..ead2f2c 100644
@@ -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) {

Benoit PAPILLAULT

Acked-by on v1 1/1

2010-02-27 14:20 UTC #1 lore raw

Quoted 13 lines · Dan Carpenter

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 <[email protected]>
---
This was found by a static check and compile tested only. Please review carefully.
drivers/net/wireless/zd1211rw/zd_mac.c +0 -0
index f14deb0..ead2f2c 100644

drivers/net/wireless/zd1211rw/zd_mac.c static void zd_mac_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb, · line 354

Quoted 6 lines

drivers/net/wireless/zd1211rw/zd_mac.c +1 -1

@@ -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);

Note: normal hardware always report a tx_status->retry >= 1. There are 2 code paths to initialize retry itself : either tx_status is NULL and then retry=1 (so we are safe), or tx_status is not NULL and retry = tx_status->retry + success >=1 (so we are safe again).

However, I wonder how we should handle if it happens that the HW reports a tx_status->retry = 0. I think ZD_ASSERT purpose is to catch programming errors, not bogus hardware. Comments?

Quoted 19 lines

drivers/net/wireless/zd1211rw/zd_mac.c +1 -2

 	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) {

drivers/net/wireless/zd1211rw/zd_mac.c void zd_mac_tx_failed(struct urb *urb) · line 433

Quoted 10 lines

drivers/net/wireless/zd1211rw/zd_mac.c +2 -3

+		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) {

Acked-by Benoit Papillault <[email protected]>

Regards,
Benoit

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walter harms

2010-02-27 17:27 UTC #2 lore raw

Quoted 29 lines · Benoit PAPILLAULT

Quoted 17 lines · Dan Carpenter
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 <[email protected]>
---
This was found by a static check and compile tested only. Please review carefully.
drivers/net/wireless/zd1211rw/zd_mac.c +0 -0
index f14deb0..ead2f2c 100644
drivers/net/wireless/zd1211rw/zd_mac.c static void zd_mac_tx_status(struct ieee80211_hw · line 355
Quoted 7 lines
drivers/net/wireless/zd1211rw/zd_mac.c +1 -1
@@ -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);
 
Note: normal hardware always report a tx_status->retry >= 1. There are 2
code paths to initialize retry itself : either tx_status is NULL and
then retry=1 (so we are safe), or tx_status is not NULL and retry > tx_status->retry + success >=1 (so we are safe again).

Quoted 3 lines

However, I wonder how we should handle if it happens that the HW reports a tx_status->retry = 0. I think ZD_ASSERT purpose is to catch programming errors, not bogus hardware. Comments?

Simply assume the worst, so far i see the patch does not add more code nor should it change normal behavier. This will help to make the code more robust.

just my 2 cents,
walter

Quoted 28 lines

drivers/net/wireless/zd1211rw/zd_mac.c +0 -0

     info->status.rates[0].idx = retries->rate[0];

     info->status.rates[0].count = 1; // (retry > 1 ? 2 : 1);

drivers/net/wireless/zd1211rw/zd_mac.c +1 -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)

drivers/net/wireless/zd1211rw/zd_mac.c +2 -4

@@ -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;

Quoted 15 lines

drivers/net/wireless/zd1211rw/zd_mac.c void zd_mac_tx_failed(struct urb *urb) · line 433
Quoted 3 lines
drivers/net/wireless/zd1211rw/zd_mac.c +0 -0
         if (final_rate != tx_status->rate) {
Acked-by Benoit Papillault <[email protected]>
Regards,
Benoit
Signature · 4 lines
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Benoit PAPILLAULT

Acked-by on v1 1/1

2010-02-27 14:27 UTC #3 lore raw

In reply to Dan Carpenter

Quoted 13 lines · Dan Carpenter

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 <[email protected]>
---
This was found by a static check and compile tested only. Please review carefully.
drivers/net/wireless/zd1211rw/zd_mac.c +0 -0
index f14deb0..ead2f2c 100644

drivers/net/wireless/zd1211rw/zd_mac.c static void zd_mac_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb, · line 354

Quoted 6 lines

drivers/net/wireless/zd1211rw/zd_mac.c +1 -1

@@ -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);

However, I wonder how we should handle if it happens that the HW reports a tx_status->retry = 0. I think ZD_ASSERT purpose is to catch programming errors, not bogus hardware. Comments?

Quoted 19 lines

drivers/net/wireless/zd1211rw/zd_mac.c +1 -2

 	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) {

drivers/net/wireless/zd1211rw/zd_mac.c void zd_mac_tx_failed(struct urb *urb) · line 433

Quoted 10 lines

drivers/net/wireless/zd1211rw/zd_mac.c +2 -3

+		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) {

Acked-by Benoit Papillault <[email protected]>

Regards,
Benoit