[PATCH] mac80211: minstrel: avoid accessing negative indices in rix_to_ndx()

[PATCH] mac80211: minstrel: avoid accessing negative indices in rix_to_ndx()

[Luciano Coelho]

If rix is not found in mi->r[], i will become -1 after the loop.  This value
is eventually used to access arrays, so we were accessing arrays with a
negative index, which is obviously not what we want to do.  This patch fixes
this potential problem.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
---
 net/mac80211/rc80211_minstrel.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index b218b98..e2dd248 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -66,7 +66,7 @@ rix_to_ndx(struct minstrel_sta_info *mi, int rix)
 	for (i = rix; i >= 0; i--)
 		if (mi->r[i].rix == rix)
 			break;
-	WARN_ON(mi->r[i].rix != rix);
+	WARN_ON(i < 0 || mi->r[i].rix != rix);
 	return i;
 }
 
@@ -181,6 +181,9 @@ minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
 			break;
 
 		ndx = rix_to_ndx(mi, ar[i].idx);
+		if (ndx < 0)
+			continue;
+
 		mi->r[ndx].attempts += ar[i].count;
 
 		if ((i != IEEE80211_TX_MAX_RATES - 1) && (ar[i + 1].idx < 0))
-- 
1.6.0.4

Re: [PATCH] mac80211: minstrel: avoid accessing negative indices in rix_to_ndx()

[Felix Fietkau]

Luciano Coelho wrote:
> If rix is not found in mi->r[], i will become -1 after the loop.  This value
> is eventually used to access arrays, so we were accessing arrays with a
> negative index, which is obviously not what we want to do.  This patch fixes
> this potential problem.
> 
> Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
> ---
>  net/mac80211/rc80211_minstrel.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
> index b218b98..e2dd248 100644
> --- a/net/mac80211/rc80211_minstrel.c
> +++ b/net/mac80211/rc80211_minstrel.c
> @@ -66,7 +66,7 @@ rix_to_ndx(struct minstrel_sta_info *mi, int rix)
>  	for (i = rix; i >= 0; i--)
>  		if (mi->r[i].rix == rix)
>  			break;
> -	WARN_ON(mi->r[i].rix != rix);
> +	WARN_ON(i < 0 || mi->r[i].rix != rix);
I believe this line could be changed to WARN_ON(i < 0), because
(mi->r[i].rix != rix) will never be true unless i < 0.
Probably not that important though.

Acked-by: Felix Fietkau <nbd@openwrt.org>

- Felix

Re: [PATCH] mac80211: minstrel: avoid accessing negative indices in rix_to_ndx()

[Luciano Coelho]

ext Felix Fietkau wrote:
> Luciano Coelho wrote:
>   
>> If rix is not found in mi->r[], i will become -1 after the loop.  This value
>> is eventually used to access arrays, so we were accessing arrays with a
>> negative index, which is obviously not what we want to do.  This patch fixes
>> this potential problem.
>>
>> Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
>> ---
>>  net/mac80211/rc80211_minstrel.c |    5 ++++-
>>  1 files changed, 4 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
>> index b218b98..e2dd248 100644
>> --- a/net/mac80211/rc80211_minstrel.c
>> +++ b/net/mac80211/rc80211_minstrel.c
>> @@ -66,7 +66,7 @@ rix_to_ndx(struct minstrel_sta_info *mi, int rix)
>>  	for (i = rix; i >= 0; i--)
>>  		if (mi->r[i].rix == rix)
>>  			break;
>> -	WARN_ON(mi->r[i].rix != rix);
>> +	WARN_ON(i < 0 || mi->r[i].rix != rix);
>>     
> I believe this line could be changed to WARN_ON(i < 0), because
> (mi->r[i].rix != rix) will never be true unless i < 0.
> Probably not that important though.
>   

That's true.  I'll change the code and send v2.  It's not that 
important, but it is code that will never be reached, so it should be 
removed.

> Acked-by: Felix Fietkau <nbd@openwrt.org>
>   

Thanks!

-- 
Cheers,
Luca.