cfg80211: always check for scan end on P2P device

If a P2P device wdev is removed while it has a scan, then the
scan completion might crash later as it is already freed by
that time. To avoid the crash always check the scan completion
when the P2P device is being removed for some reason. If the
driver already canceled it, don't want and free it, otherwise
warn and leak it to avoid later crashes.

In order to do this, locking needs to be changed away from the
rdev mutex (which can't always be guaranteed). For now, use
the sched_scan_mtx instead, I'll rename it to just scan_mtx in
a later patch.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 27 insertions, 25 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index d44ab216c0e..58e13a8c95f 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -4702,14 +4702,19 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 	if (!rdev->ops->scan)
 		return -EOPNOTSUPP;
 
-	if (rdev->scan_req)
-		return -EBUSY;
+	mutex_lock(&rdev->sched_scan_mtx);
+	if (rdev->scan_req) {
+		err = -EBUSY;
+		goto unlock;
+	}
 
 	if (info->attrs[NL80211_ATTR_SCAN_FREQUENCIES]) {
 		n_channels = validate_scan_freqs(
 				info->attrs[NL80211_ATTR_SCAN_FREQUENCIES]);
-		if (!n_channels)
-			return -EINVAL;
+		if (!n_channels) {
+			err = -EINVAL;
+			goto unlock;
+		}
 	} else {
 		enum ieee80211_band band;
 		n_channels = 0;
@@ -4723,23 +4728,29 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 		nla_for_each_nested(attr, info->attrs[NL80211_ATTR_SCAN_SSIDS], tmp)
 			n_ssids++;
 
-	if (n_ssids > wiphy->max_scan_ssids)
-		return -EINVAL;
+	if (n_ssids > wiphy->max_scan_ssids) {
+		err = -EINVAL;
+		goto unlock;
+	}
 
 	if (info->attrs[NL80211_ATTR_IE])
 		ie_len = nla_len(info->attrs[NL80211_ATTR_IE]);
 	else
 		ie_len = 0;
 
-	if (ie_len > wiphy->max_scan_ie_len)
-		return -EINVAL;
+	if (ie_len > wiphy->max_scan_ie_len) {
+		err = -EINVAL;
+		goto unlock;
+	}
 
 	request = kzalloc(sizeof(*request)
 			+ sizeof(*request->ssids) * n_ssids
 			+ sizeof(*request->channels) * n_channels
 			+ ie_len, GFP_KERNEL);
-	if (!request)
-		return -ENOMEM;
+	if (!request) {
+		err = -ENOMEM;
+		goto unlock;
+	}
 
 	if (n_ssids)
 		request->ssids = (void *)&request->channels[n_channels];
@@ -4876,6 +4887,8 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 		kfree(request);
 	}
 
+ unlock:
+	mutex_unlock(&rdev->sched_scan_mtx);
 	return err;
 }
 
@@ -7749,20 +7762,9 @@ static int nl80211_stop_p2p_device(struct sk_buff *skb, struct genl_info *info)
 	if (!rdev->ops->stop_p2p_device)
 		return -EOPNOTSUPP;
 
-	if (!wdev->p2p_started)
-		return 0;
-
-	rdev_stop_p2p_device(rdev, wdev);
-	wdev->p2p_started = false;
-
-	mutex_lock(&rdev->devlist_mtx);
-	rdev->opencount--;
-	mutex_unlock(&rdev->devlist_mtx);
-
-	if (WARN_ON(rdev->scan_req && rdev->scan_req->wdev == wdev)) {
-		rdev->scan_req->aborted = true;
-		___cfg80211_scan_done(rdev, true);
-	}
+	mutex_lock(&rdev->sched_scan_mtx);
+	cfg80211_stop_p2p_device(rdev, wdev);
+	mutex_unlock(&rdev->sched_scan_mtx);
 
 	return 0;
 }
@@ -8486,7 +8488,7 @@ static int nl80211_add_scan_req(struct sk_buff *msg,
 	struct nlattr *nest;
 	int i;
 
-	ASSERT_RDEV_LOCK(rdev);
+	lockdep_assert_held(&rdev->sched_scan_mtx);
 
 	if (WARN_ON(!req))
 		return 0;