109 lines
3.3 KiB
Diff
109 lines
3.3 KiB
Diff
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Subject: [PATCH] cfg80211: fix deadlock
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From: Johannes Berg <johannes@sipsolutions.net>
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To: John Linville <linville@tuxdriver.com>
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Cc: linux-wireless <linux-wireless@vger.kernel.org>,
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Christian Lamparter <chunkeey@web.de>
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Content-Type: text/plain
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Date: Sun, 16 Aug 2009 13:32:38 +0200
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Message-Id: <1250422358.17522.0.camel@johannes.local>
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Mime-Version: 1.0
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X-Mailer: Evolution 2.27.90
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Content-Transfer-Encoding: 7bit
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Sender: linux-wireless-owner@vger.kernel.org
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Precedence: bulk
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List-ID: <linux-wireless.vger.kernel.org>
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X-Mailing-List: linux-wireless@vger.kernel.org
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When removing an interface with nl80211, cfg80211 will
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deadlock in the netdev notifier because we're already
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holding rdev->mtx and try to acquire it again to verify
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the scan has been done.
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This bug was introduced by my patch
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"cfg80211: check for and abort dangling scan requests".
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To fix this, move the dangling scan request check into
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wiphy_unregister(). This will not be able to catch all
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cases right away, but if the scan problem happens with
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a manual ifdown or so it will be possible to remedy it
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by removing the module/device.
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Additionally, add comments about the deadlock scenario.
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Reported-by: Christian Lamparter <chunkeey@web.de>
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Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
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---
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net/wireless/core.c | 32 +++++++++++++++++++-------------
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1 file changed, 19 insertions(+), 13 deletions(-)
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--- a/net/wireless/core.c
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+++ b/net/wireless/core.c
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@@ -586,9 +586,15 @@ void wiphy_unregister(struct wiphy *wiph
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* get to lock contention here if userspace issues a command
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* that identified the hardware by wiphy index.
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*/
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- mutex_lock(&rdev->mtx);
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- /* unlock again before freeing */
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- mutex_unlock(&rdev->mtx);
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+ cfg80211_lock_rdev(rdev);
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+
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+ if (WARN_ON(rdev->scan_req)) {
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+ rdev->scan_req->aborted = true;
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+ ___cfg80211_scan_done(rdev);
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+ }
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+
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+ cfg80211_unlock_rdev(rdev);
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+ flush_work(&rdev->scan_done_wk);
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cfg80211_debugfs_rdev_del(rdev);
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@@ -603,9 +609,7 @@ void wiphy_unregister(struct wiphy *wiph
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mutex_unlock(&cfg80211_mutex);
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- flush_work(&rdev->scan_done_wk);
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cancel_work_sync(&rdev->conn_work);
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- kfree(rdev->scan_req);
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flush_work(&rdev->event_work);
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}
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EXPORT_SYMBOL(wiphy_unregister);
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@@ -653,6 +657,11 @@ static int cfg80211_netdev_notifier_call
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switch (state) {
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case NETDEV_REGISTER:
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+ /*
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+ * NB: cannot take rdev->mtx here because this may be
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+ * called within code protected by it when interfaces
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+ * are added with nl80211.
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+ */
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mutex_init(&wdev->mtx);
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INIT_LIST_HEAD(&wdev->event_list);
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spin_lock_init(&wdev->event_lock);
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@@ -730,13 +739,11 @@ static int cfg80211_netdev_notifier_call
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#endif
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break;
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case NETDEV_UNREGISTER:
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- cfg80211_lock_rdev(rdev);
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-
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- if (WARN_ON(rdev->scan_req && rdev->scan_req->dev == dev)) {
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- rdev->scan_req->aborted = true;
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- ___cfg80211_scan_done(rdev);
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- }
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-
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+ /*
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+ * NB: cannot take rdev->mtx here because this may be
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+ * called within code protected by it when interfaces
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+ * are removed with nl80211.
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+ */
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mutex_lock(&rdev->devlist_mtx);
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/*
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* It is possible to get NETDEV_UNREGISTER
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@@ -755,7 +762,6 @@ static int cfg80211_netdev_notifier_call
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#endif
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}
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mutex_unlock(&rdev->devlist_mtx);
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- cfg80211_unlock_rdev(rdev);
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break;
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case NETDEV_PRE_UP:
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if (!(wdev->wiphy->interface_modes & BIT(wdev->iftype)))
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