diff mbox

[RFC,2/2] mac80211: Fix bss ref leak.

Message ID 1371504746-8476-2-git-send-email-greearb@candelatech.com (mailing list archive)
State Not Applicable, archived
Headers show

Commit Message

Ben Greear June 17, 2013, 9:32 p.m. UTC 
From: Ben Greear <greearb@candelatech.com>

Some of the calls to ieee80211_destroy_assoc_data should
be putting the bss reference and were not.  Add boolean
argument to tell that method whether or not it should put
the reference and fix calling code appropriately.

Grab the bss reference where the pointer is assigned
to make it easier to properly do reference counting.

Also add some comments to help clarify the bss ref-counting
logic.

Signed-off-by: Ben Greear <greearb@candelatech.com>
---
 net/mac80211/mlme.c |   34 +++++++++++++++++++++++++---------
 net/mac80211/scan.c |    6 ++++++
 2 files changed, 31 insertions(+), 9 deletions(-)

Comments

Johannes Berg June 18, 2013, 3:26 p.m. UTC | #1 
On Mon, 2013-06-17 at 14:32 -0700, greearb@candelatech.com wrote:

>  static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
> -					 bool assoc)
> +					 bool assoc, bool put_bss)

Do we _really_ need another argument? Shouldn't it always be put in the
non-assoc case anyway, at least if non-NULL?

> @@ -2415,6 +2415,10 @@ static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
>  		ieee80211_vif_release_channel(sdata);
>  	}
>  
> +	if (put_bss)
> +		cfg80211_put_bss(sdata->local->hw.wiphy, assoc_data->bss);
> +
> +

just one blank line

> +	/** bss will be passed back to calling code, and that code must
> +	 * deal with properly putting the reference.
> +	 */

/** is for kernel-doc only

>  	return RX_MGMT_CFG80211_RX_ASSOC;

You're working on some pretty old code here ... If you want this to be
in stable the patch really needs to be smaller, I think. And for
mac80211-next this can't apply.

johannes

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Ben Greear June 18, 2013, 3:38 p.m. UTC | #2 
On 06/18/2013 08:26 AM, Johannes Berg wrote:
> On Mon, 2013-06-17 at 14:32 -0700, greearb@candelatech.com wrote:
>
>>   static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
>> -					 bool assoc)
>> +					 bool assoc, bool put_bss)
>
> Do we _really_ need another argument? Shouldn't it always be put in the
> non-assoc case anyway, at least if non-NULL?

I can check if that is the case...

>
>> @@ -2415,6 +2415,10 @@ static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
>>   		ieee80211_vif_release_channel(sdata);
>>   	}
>>
>> +	if (put_bss)
>> +		cfg80211_put_bss(sdata->local->hw.wiphy, assoc_data->bss);
>> +
>> +
>
> just one blank line
>
>> +	/** bss will be passed back to calling code, and that code must
>> +	 * deal with properly putting the reference.
>> +	 */
>
> /** is for kernel-doc only
>
>>   	return RX_MGMT_CFG80211_RX_ASSOC;
>
> You're working on some pretty old code here ... If you want this to be
> in stable the patch really needs to be smaller, I think. And for
> mac80211-next this can't apply.

I'm working on 3.9.6.  When I get the problems fixed here, I can help
port this to whatever is the upstream kernel.

I'm not certain this is worth bothering with for stable anyway.
It seems the leaks are not too bad in general use cases,
and piddling around with code this tricky code could
introduce worse bugs that we may not immediately notice.

Thanks,
Ben

>
> johannes
>
Ben Greear June 18, 2013, 4:33 p.m. UTC | #3 
On 06/18/2013 08:26 AM, Johannes Berg wrote:
> On Mon, 2013-06-17 at 14:32 -0700, greearb@candelatech.com wrote:
>
>>   static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
>> -					 bool assoc)
>> +					 bool assoc, bool put_bss)
>
> Do we _really_ need another argument? Shouldn't it always be put in the
> non-assoc case anyway, at least if non-NULL?

I don't think so.  Check out the ieee80211_rx_mgmt_assoc_resp method.

  	if (status_code != WLAN_STATUS_SUCCESS) {
		sdata_info(sdata, "%pM denied association (code=%d)\n",
			   mgmt->sa, status_code);
		ieee80211_destroy_assoc_data(sdata, false, false);

This passes in false as 'assoc', but we should not free bss here because
it is being passed back to the calling method, and the return
code of RX_MGMT_CFG80211_RX_ASSOC means bss should eventually
be consumed by the cfg80211 logic.

Of course, this is all 'as far as I can tell'.

I sort of like the second boolean because it forces the caller to
think about whether bss should be freed or not...

Thanks,
Ben
Johannes Berg June 19, 2013, 2:13 p.m. UTC | #4 
On Tue, 2013-06-18 at 09:33 -0700, Ben Greear wrote:
> On 06/18/2013 08:26 AM, Johannes Berg wrote:
> > On Mon, 2013-06-17 at 14:32 -0700, greearb@candelatech.com wrote:
> >
> >>   static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
> >> -					 bool assoc)
> >> +					 bool assoc, bool put_bss)
> >
> > Do we _really_ need another argument? Shouldn't it always be put in the
> > non-assoc case anyway, at least if non-NULL?
> 
> I don't think so.  Check out the ieee80211_rx_mgmt_assoc_resp method.
> 
>   	if (status_code != WLAN_STATUS_SUCCESS) {
> 		sdata_info(sdata, "%pM denied association (code=%d)\n",
> 			   mgmt->sa, status_code);
> 		ieee80211_destroy_assoc_data(sdata, false, false);
> 
> This passes in false as 'assoc', but we should not free bss here because
> it is being passed back to the calling method, and the return
> code of RX_MGMT_CFG80211_RX_ASSOC means bss should eventually
> be consumed by the cfg80211 logic.
> 
> Of course, this is all 'as far as I can tell'.
> 
> I sort of like the second boolean because it forces the caller to
> think about whether bss should be freed or not...

I just posted a patch to hand it back and never free it in mac80211 at
all, that also allows cfg80211_hold_bss() it across the assoc process
which fixes a (possibly more theoretical) expiry issue.

johannes

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diff mbox

Patch

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 6510790..732eda0 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2400,7 +2400,7 @@  static void ieee80211_get_rates(struct ieee80211_supported_band *sband,
 }
 
 static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
-					 bool assoc)
+					 bool assoc, bool put_bss)
 {
 	struct ieee80211_mgd_assoc_data *assoc_data = sdata->u.mgd.assoc_data;
 
@@ -2415,6 +2415,10 @@  static void ieee80211_destroy_assoc_data(struct ieee80211_sub_if_data *sdata,
 		ieee80211_vif_release_channel(sdata);
 	}
 
+	if (put_bss)
+		cfg80211_put_bss(sdata->local->hw.wiphy, assoc_data->bss);
+
+
 	kfree(assoc_data);
 	sdata->u.mgd.assoc_data = NULL;
 }
@@ -2587,6 +2591,7 @@  static bool ieee80211_assoc_success(struct ieee80211_sub_if_data *sdata,
 	return true;
 }
 
+/** Calling code must dispose of bss reference if it is not NULL. */
 static enum rx_mgmt_action __must_check
 ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
 			     struct ieee80211_mgmt *mgmt, size_t len,
@@ -2643,17 +2648,20 @@  ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
 		return RX_MGMT_NONE;
 	}
 
+	/** bss will be passed back to calling code, and that code must
+	 * deal with properly putting the reference.
+	 */
 	*bss = assoc_data->bss;
 
 	if (status_code != WLAN_STATUS_SUCCESS) {
 		sdata_info(sdata, "%pM denied association (code=%d)\n",
 			   mgmt->sa, status_code);
-		ieee80211_destroy_assoc_data(sdata, false);
+		ieee80211_destroy_assoc_data(sdata, false, false);
 	} else {
 		if (!ieee80211_assoc_success(sdata, *bss, mgmt, len)) {
 			/* oops -- internal error -- send timeout for now */
-			ieee80211_destroy_assoc_data(sdata, false);
-			cfg80211_put_bss(sdata->local->hw.wiphy, *bss);
+			ieee80211_destroy_assoc_data(sdata, false, true);
+			*bss = NULL; /* Ensure no stale references */
 			return RX_MGMT_CFG80211_ASSOC_TIMEOUT;
 		}
 		sdata_info(sdata, "associated\n");
@@ -2663,7 +2671,7 @@  ieee80211_rx_mgmt_assoc_resp(struct ieee80211_sub_if_data *sdata,
 		 * recalc after assoc_data is NULL but before associated
 		 * is set can cause the interface to go idle
 		 */
-		ieee80211_destroy_assoc_data(sdata, true);
+		ieee80211_destroy_assoc_data(sdata, true, false);
 	}
 
 	return RX_MGMT_CFG80211_RX_ASSOC;
@@ -3105,6 +3113,9 @@  void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
 		break;
 	case IEEE80211_STYPE_ASSOC_RESP:
 	case IEEE80211_STYPE_REASSOC_RESP:
+		/* One way or another, must eventually put bss reference
+		 * if it is not NULL.
+		 */
 		rma = ieee80211_rx_mgmt_assoc_resp(sdata, mgmt, skb->len, &bss);
 		break;
 	case IEEE80211_STYPE_ACTION:
@@ -3136,6 +3147,9 @@  void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
 		cfg80211_send_rx_assoc(sdata->dev, bss, (u8 *)mgmt, skb->len);
 		break;
 	case RX_MGMT_CFG80211_ASSOC_TIMEOUT:
+		/* bss reference is already put at this point, see
+		 * 'internal-error' comment in ieee80211_rx_mgmt_assoc_resp
+		 */
 		cfg80211_send_assoc_timeout(sdata->dev, mgmt->bssid);
 		break;
 	case RX_MGMT_CFG80211_TX_DEAUTH:
@@ -3385,7 +3399,7 @@  void ieee80211_sta_work(struct ieee80211_sub_if_data *sdata)
 
 			memcpy(bssid, ifmgd->assoc_data->bss->bssid, ETH_ALEN);
 
-			ieee80211_destroy_assoc_data(sdata, false);
+			ieee80211_destroy_assoc_data(sdata, false, true);
 
 			mutex_unlock(&ifmgd->mtx);
 			cfg80211_send_assoc_timeout(sdata->dev, bssid);
@@ -3935,6 +3949,7 @@  int ieee80211_mgd_auth(struct ieee80211_sub_if_data *sdata,
 		return -ENOMEM;
 
 	auth_data->bss = req->bss;
+	cfg80211_ref_bss(local->hw.wiphy, auth_data->bss);
 
 	if (req->sae_data_len >= 4) {
 		__le16 *pos = (__le16 *) req->sae_data;
@@ -3998,8 +4013,6 @@  int ieee80211_mgd_auth(struct ieee80211_sub_if_data *sdata,
 		goto err_clear;
 	}
 
-	/* hold our own reference */
-	cfg80211_ref_bss(local->hw.wiphy, auth_data->bss);
 	err = 0;
 	goto out_unlock;
 
@@ -4008,6 +4021,7 @@  int ieee80211_mgd_auth(struct ieee80211_sub_if_data *sdata,
 	ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BSSID);
 	ifmgd->auth_data = NULL;
  err_free:
+	cfg80211_put_bss(sdata->local->hw.wiphy, auth_data->bss);
 	kfree(auth_data);
  out_unlock:
 	mutex_unlock(&ifmgd->mtx);
@@ -4129,6 +4143,7 @@  int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 	}
 
 	assoc_data->bss = req->bss;
+	cfg80211_ref_bss(sdata->local->hw.wiphy, assoc_data->bss);
 
 	if (ifmgd->req_smps == IEEE80211_SMPS_AUTOMATIC) {
 		if (ifmgd->powersave)
@@ -4259,6 +4274,7 @@  int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
  err_clear:
 	memset(ifmgd->bssid, 0, ETH_ALEN);
 	ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_BSSID);
+	cfg80211_put_bss(sdata->local->hw.wiphy, assoc_data->bss);
 	ifmgd->assoc_data = NULL;
  err_free:
 	kfree(assoc_data);
@@ -4364,7 +4380,7 @@  void ieee80211_mgd_stop(struct ieee80211_sub_if_data *sdata)
 
 	mutex_lock(&ifmgd->mtx);
 	if (ifmgd->assoc_data)
-		ieee80211_destroy_assoc_data(sdata, false);
+		ieee80211_destroy_assoc_data(sdata, false, true);
 	if (ifmgd->auth_data)
 		ieee80211_destroy_auth_data(sdata, false);
 	del_timer_sync(&ifmgd->timer);
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 0b6434b..e0fcb4a 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -55,6 +55,9 @@  static bool is_uapsd_supported(struct ieee802_11_elems *elems)
 	return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
 }
 
+/** Must (eventually) put the returned value to keep from leaking
+ * a reference to the bss.
+ */
 struct ieee80211_bss *
 ieee80211_bss_info_update(struct ieee80211_local *local,
 			  struct ieee80211_rx_status *rx_status,
@@ -73,6 +76,9 @@  ieee80211_bss_info_update(struct ieee80211_local *local,
 	else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
 		signal = (rx_status->signal * 100) / local->hw.max_signal;
 
+	/* We now own a reference to cbss, have to make sure we
+	 * put it later.
+	 */
 	cbss = cfg80211_inform_bss_frame(local->hw.wiphy, channel,
 					 mgmt, len, signal, GFP_ATOMIC);
 	if (!cbss)