From d07bfd8b6f20a81d7ec65c50f35b053d9e3aa740 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 7 Mar 2011 15:48:41 +0100 Subject: [PATCH] mac80211: fix scan race, simplify code The scan code has a race that Michael reported he ran into, but it's easy to fix while at the same time simplifying the code. The race resulted in the following warning: ------------[ cut here ]------------ WARNING: at net/mac80211/scan.c:310 ieee80211_rx_bss_free+0x20c/0x4b8 [mac80211]() Modules linked in: [...] [] (unwind_backtrace+0x0/0xe0) from [] (warn_slowpath_common+0x4c/0x64) [... backtrace wasn't useful ...] Reported-by: Michael Buesch Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- net/mac80211/scan.c | 64 ++++++++++++++++++++--------------------------------- 1 file changed, 24 insertions(+), 40 deletions(-) diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c index 8429545..489b6ad 100644 --- a/net/mac80211/scan.c +++ b/net/mac80211/scan.c @@ -258,10 +258,12 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local) return true; } -static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted, +static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted, bool was_hw_scan) { struct ieee80211_local *local = hw_to_local(hw); + bool on_oper_chan; + bool enable_beacons = false; lockdep_assert_held(&local->mtx); @@ -275,12 +277,12 @@ static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted, aborted = true; if (WARN_ON(!local->scan_req)) - return false; + return; if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) { int rc = drv_hw_scan(local, local->scan_sdata, local->hw_scan_req); if (rc == 0) - return false; + return; } kfree(local->hw_scan_req); @@ -294,26 +296,11 @@ static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted, local->scanning = 0; local->scan_channel = NULL; - return true; -} - -static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw, - bool was_hw_scan) -{ - struct ieee80211_local *local = hw_to_local(hw); - bool on_oper_chan; - bool enable_beacons = false; - - mutex_lock(&local->mtx); on_oper_chan = ieee80211_cfg_on_oper_channel(local); - WARN_ON(local->scanning & (SCAN_SW_SCANNING | SCAN_HW_SCANNING)); - - if (was_hw_scan || !on_oper_chan) { - if (WARN_ON(local->scan_channel)) - local->scan_channel = NULL; + if (was_hw_scan || !on_oper_chan) ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL); - } else + else /* Set power back to normal operating levels. */ ieee80211_hw_config(local, 0); @@ -331,7 +318,6 @@ static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw, } ieee80211_recalc_idle(local); - mutex_unlock(&local->mtx); ieee80211_mlme_notify_scan_completed(local); ieee80211_ibss_notify_scan_completed(local); @@ -686,12 +672,14 @@ void ieee80211_scan_work(struct work_struct *work) { struct ieee80211_local *local = container_of(work, struct ieee80211_local, scan_work.work); - struct ieee80211_sub_if_data *sdata = local->scan_sdata; + struct ieee80211_sub_if_data *sdata; unsigned long next_delay = 0; - bool aborted, hw_scan, finish; + bool aborted, hw_scan; mutex_lock(&local->mtx); + sdata = local->scan_sdata; + if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) { aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning); goto out_complete; @@ -755,17 +743,11 @@ void ieee80211_scan_work(struct work_struct *work) } while (next_delay == 0); ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay); - mutex_unlock(&local->mtx); - return; + goto out; out_complete: hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning); - finish = __ieee80211_scan_completed(&local->hw, aborted, hw_scan); - mutex_unlock(&local->mtx); - if (finish) - __ieee80211_scan_completed_finish(&local->hw, hw_scan); - return; - + __ieee80211_scan_completed(&local->hw, aborted, hw_scan); out: mutex_unlock(&local->mtx); } @@ -835,7 +817,6 @@ int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata, void ieee80211_scan_cancel(struct ieee80211_local *local) { bool abortscan; - bool finish = false; /* * We are only canceling software scan, or deferred scan that was not @@ -855,14 +836,17 @@ void ieee80211_scan_cancel(struct ieee80211_local *local) mutex_lock(&local->mtx); abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning); - if (abortscan) - finish = __ieee80211_scan_completed(&local->hw, true, false); - mutex_unlock(&local->mtx); - if (abortscan) { - /* The scan is canceled, but stop work from being pending */ - cancel_delayed_work_sync(&local->scan_work); + /* + * The scan is canceled, but stop work from being pending. + * + * If the work is currently running, it must be blocked on + * the mutex, but we'll set scan_sdata = NULL and it'll + * simply exit once it acquires the mutex. + */ + cancel_delayed_work(&local->scan_work); + /* and clean up */ + __ieee80211_scan_completed(&local->hw, true, false); } - if (finish) - __ieee80211_scan_completed_finish(&local->hw, false); + mutex_unlock(&local->mtx); } -- 2.7.4