From fe20b39ec32e975f1054c0b7866c873a954adf05 Mon Sep 17 00:00:00 2001 From: Eliad Peller Date: Tue, 12 Jun 2012 12:53:13 +0300 Subject: cfg80211: fix potential deadlock in regulatory reg_timeout_work() calls restore_regulatory_settings() which takes cfg80211_mutex. reg_set_request_processed() already holds cfg80211_mutex before calling cancel_delayed_work_sync(reg_timeout), so it might deadlock. Call the async cancel_delayed_work instead, in order to avoid the potential deadlock. This is the relevant lockdep warning: cfg80211: Calling CRDA for country: XX ====================================================== [ INFO: possible circular locking dependency detected ] 3.4.0-rc5-wl+ #26 Not tainted ------------------------------------------------------- kworker/0:2/1391 is trying to acquire lock: (cfg80211_mutex){+.+.+.}, at: [] restore_regulatory_settings+0x34/0x418 [cfg80211] but task is already holding lock: ((reg_timeout).work){+.+...}, at: [] process_one_work+0x1f0/0x480 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 ((reg_timeout).work){+.+...}: [] validate_chain+0xb94/0x10f0 [] __lock_acquire+0x8c8/0x9b0 [] lock_acquire+0xf0/0x114 [] wait_on_work+0x4c/0x154 [] __cancel_work_timer+0xd4/0x11c [] cancel_delayed_work_sync+0x1c/0x20 [] reg_set_request_processed+0x50/0x78 [cfg80211] [] set_regdom+0x550/0x600 [cfg80211] [] nl80211_set_reg+0x218/0x258 [cfg80211] [] genl_rcv_msg+0x1a8/0x1e8 [] netlink_rcv_skb+0x5c/0xc0 [] genl_rcv+0x28/0x34 [] netlink_unicast+0x15c/0x228 [] netlink_sendmsg+0x218/0x298 [] sock_sendmsg+0xa4/0xc0 [] __sys_sendmsg+0x1e4/0x268 [] sys_sendmsg+0x4c/0x70 [] ret_fast_syscall+0x0/0x3c -> #1 (reg_mutex){+.+.+.}: [] validate_chain+0xb94/0x10f0 [] __lock_acquire+0x8c8/0x9b0 [] lock_acquire+0xf0/0x114 [] mutex_lock_nested+0x48/0x320 [] reg_todo+0x30/0x538 [cfg80211] [] process_one_work+0x2a0/0x480 [] worker_thread+0x1bc/0x2bc [] kthread+0x98/0xa4 [] kernel_thread_exit+0x0/0x8 -> #0 (cfg80211_mutex){+.+.+.}: [] print_circular_bug+0x68/0x2cc [] validate_chain+0x978/0x10f0 [] __lock_acquire+0x8c8/0x9b0 [] lock_acquire+0xf0/0x114 [] mutex_lock_nested+0x48/0x320 [] restore_regulatory_settings+0x34/0x418 [cfg80211] [] reg_timeout_work+0x1c/0x20 [cfg80211] [] process_one_work+0x2a0/0x480 [] worker_thread+0x1bc/0x2bc [] kthread+0x98/0xa4 [] kernel_thread_exit+0x0/0x8 other info that might help us debug this: Chain exists of: cfg80211_mutex --> reg_mutex --> (reg_timeout).work Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((reg_timeout).work); lock(reg_mutex); lock((reg_timeout).work); lock(cfg80211_mutex); *** DEADLOCK *** 2 locks held by kworker/0:2/1391: #0: (events){.+.+.+}, at: [] process_one_work+0x1f0/0x480 #1: ((reg_timeout).work){+.+...}, at: [] process_one_work+0x1f0/0x480 stack backtrace: [] (unwind_backtrace+0x0/0x12c) from [] (dump_stack+0x20/0x24) [] (dump_stack+0x20/0x24) from [] (print_circular_bug+0x280/0x2cc) [] (print_circular_bug+0x280/0x2cc) from [] (validate_chain+0x978/0x10f0) [] (validate_chain+0x978/0x10f0) from [] (__lock_acquire+0x8c8/0x9b0) [] (__lock_acquire+0x8c8/0x9b0) from [] (lock_acquire+0xf0/0x114) [] (lock_acquire+0xf0/0x114) from [] (mutex_lock_nested+0x48/0x320) [] (mutex_lock_nested+0x48/0x320) from [] (restore_regulatory_settings+0x34/0x418 [cfg80211]) [] (restore_regulatory_settings+0x34/0x418 [cfg80211]) from [] (reg_timeout_work+0x1c/0x20 [cfg80211]) [] (reg_timeout_work+0x1c/0x20 [cfg80211]) from [] (process_one_work+0x2a0/0x480) [] (process_one_work+0x2a0/0x480) from [] (worker_thread+0x1bc/0x2bc) [] (worker_thread+0x1bc/0x2bc) from [] (kthread+0x98/0xa4) [] (kthread+0x98/0xa4) from [] (kernel_thread_exit+0x0/0x8) cfg80211: Calling CRDA to update world regulatory domain cfg80211: World regulatory domain updated: cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) cfg80211: (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) Cc: stable@kernel.org Signed-off-by: Eliad Peller Signed-off-by: Johannes Berg --- net/wireless/reg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/wireless/reg.c b/net/wireless/reg.c index 15f347477a99..baf5704740ee 100644 --- a/net/wireless/reg.c +++ b/net/wireless/reg.c @@ -1389,7 +1389,7 @@ static void reg_set_request_processed(void) spin_unlock(®_requests_lock); if (last_request->initiator == NL80211_REGDOM_SET_BY_USER) - cancel_delayed_work_sync(®_timeout); + cancel_delayed_work(®_timeout); if (need_more_processing) schedule_work(®_work); -- cgit v1.2.3