Subject: Re: [PATCH] net: mac80211: tx.c: be sure of 'sdata->vif.type' must be NL80211_IFTYPE_AP when be in NL80211_IFTYPE_AP case

From: Chen Gang <[email-masked]>
Date: Sat, 30 Nov 2013 19:59:02 +0800

On 11/29/2013 11:38 PM, Johannes Berg wrote:
> 
>> +++ b/net/mac80211/tx.c
>> @@ -1814,8 +1814,9 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
>>  			break;
>>  		/* fall through */
>>  	case NL80211_IFTYPE_AP:
>> -		if (sdata->vif.type == NL80211_IFTYPE_AP)
>> -			chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
>> +		if (sdata->vif.type != NL80211_IFTYPE_AP)
>> +			goto fail_rcu;
>> +		chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
> 
> This change is completely wrong.
> 

Oh, it is.

Hmm... for me, this work flow still can be implemented with a little
clearer way (at least it will avoid related warning):

-------------------------diff begin------------------------------

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index c558b24..7076128 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1810,14 +1810,14 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
 		if (!chanctx_conf)
 			goto fail_rcu;
 		band = chanctx_conf->def.chan->band;
-		if (sta)
-			break;
-		/* fall through */
+		if (!sta)
+			goto try_next;
+		break;
 	case NL80211_IFTYPE_AP:
-		if (sdata->vif.type == NL80211_IFTYPE_AP)
-			chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
+		chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
 		if (!chanctx_conf)
 			goto fail_rcu;
+try_next:
 		fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS);
 		/* DA BSSID SA */
 		memcpy(hdr.addr1, skb->data, ETH_ALEN);

-------------------------diff end--------------------------------

Thanks.
-- 
Chen Gang