linux-kernel - [PATCH 3.11 15/94] mac80211: correctly close cancelled scans

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Message-Id: <20131109065205.327135501@linuxfoundation.org>
Date:	Fri,  8 Nov 2013 22:51:21 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
	Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 3.11 15/94] mac80211: correctly close cancelled scans

3.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Emmanuel Grumbach <emmanuel.grumbach@...el.com>

commit a754055a1296fcbe6f32de3a5eaca6efb2fd1865 upstream.

__ieee80211_scan_completed is called from a worker. This
means that the following flow is possible.

 * driver calls ieee80211_scan_completed
 * mac80211 cancels the scan (that is already complete)
 * __ieee80211_scan_completed runs

When scan_work will finally run, it will see that the scan
hasn't been aborted and might even trigger another scan on
another band. This leads to a situation where cfg80211's
scan is not done and no further scan can be issued.

Fix this by setting a new flag when a HW scan is being
cancelled so that no other scan will be triggered.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/mac80211/ieee80211_i.h |    3 +++
 net/mac80211/scan.c        |   19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -858,6 +858,8 @@ struct tpt_led_trigger {
  *	that the scan completed.
  * @SCAN_ABORTED: Set for our scan work function when the driver reported
  *	a scan complete for an aborted scan.
+ * @SCAN_HW_CANCELLED: Set for our scan work function when the scan is being
+ *	cancelled.
  */
 enum {
 	SCAN_SW_SCANNING,
@@ -865,6 +867,7 @@ enum {
 	SCAN_ONCHANNEL_SCANNING,
 	SCAN_COMPLETED,
 	SCAN_ABORTED,
+	SCAN_HW_CANCELLED,
 };
 
 /**
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -211,6 +211,9 @@ static bool ieee80211_prep_hw_scan(struc
 	enum ieee80211_band band;
 	int i, ielen, n_chans;
 
+	if (test_bit(SCAN_HW_CANCELLED, &local->scanning))
+		return false;
+
 	do {
 		if (local->hw_scan_band == IEEE80211_NUM_BANDS)
 			return false;
@@ -887,7 +890,23 @@ void ieee80211_scan_cancel(struct ieee80
 	if (!local->scan_req)
 		goto out;
 
+	/*
+	 * We have a scan running and the driver already reported completion,
+	 * but the worker hasn't run yet or is stuck on the mutex - mark it as
+	 * cancelled.
+	 */
+	if (test_bit(SCAN_HW_SCANNING, &local->scanning) &&
+	    test_bit(SCAN_COMPLETED, &local->scanning)) {
+		set_bit(SCAN_HW_CANCELLED, &local->scanning);
+		goto out;
+	}
+
 	if (test_bit(SCAN_HW_SCANNING, &local->scanning)) {
+		/*
+		 * Make sure that __ieee80211_scan_completed doesn't trigger a
+		 * scan on another band.
+		 */
+		set_bit(SCAN_HW_CANCELLED, &local->scanning);
 		if (local->ops->cancel_hw_scan)
 			drv_cancel_hw_scan(local,
 				rcu_dereference_protected(local->scan_sdata,


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