====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc3-next-20200903-syzkaller #0 Not tainted ------------------------------------------------------ kworker/u4:4/1100 is trying to acquire lock: ffff8880aa063d38 ((wq_completion)events){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x13e0 kernel/workqueue.c:2777 but task is already holding lock: ffffffff8a87d730 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xb10 net/core/net_namespace.c:565 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (pernet_ops_rwsem){++++}-{3:3}: down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 unregister_netdevice_notifier+0x1e/0x170 net/core/dev.c:1861 bcm_release+0x94/0x750 net/can/bcm.c:1474 __sock_release+0xcd/0x280 net/socket.c:596 sock_close+0x18/0x20 net/socket.c:1277 __fput+0x285/0x920 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:141 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop kernel/entry/common.c:140 [inline] exit_to_user_mode_prepare+0x1e1/0x200 kernel/entry/common.c:167 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:242 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}: down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 inode_lock include/linux/fs.h:779 [inline] __sock_release+0x86/0x280 net/socket.c:595 sock_close+0x18/0x20 net/socket.c:1277 __fput+0x285/0x920 fs/file_table.c:281 delayed_fput+0x56/0x70 fs/file_table.c:309 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 -> #1 ((delayed_fput_work).work){+.+.}-{0:0}: process_one_work+0x8bb/0x1670 kernel/workqueue.c:2245 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 -> #0 ((wq_completion)events){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x29bb/0x5570 kernel/locking/lockdep.c:4426 lock_acquire+0x1f3/0xae0 kernel/locking/lockdep.c:5006 flush_workqueue+0x110/0x13e0 kernel/workqueue.c:2780 flush_scheduled_work include/linux/workqueue.h:597 [inline] tipc_exit_net+0x47/0x2a0 net/tipc/core.c:116 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:186 cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:603 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 other info that might help us debug this: Chain exists of: (wq_completion)events --> &sb->s_type->i_mutex_key#12 --> pernet_ops_rwsem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(pernet_ops_rwsem); lock(&sb->s_type->i_mutex_key#12); lock(pernet_ops_rwsem); lock((wq_completion)events); *** DEADLOCK *** 3 locks held by kworker/u4:4/1100: #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8880a97b9138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240 #1: ffffc90004387da8 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244 #2: ffffffff8a87d730 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xb10 net/core/net_namespace.c:565 stack backtrace: CPU: 1 PID: 1100 Comm: kworker/u4:4 Not tainted 5.9.0-rc3-next-20200903-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: netns cleanup_net Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 check_noncircular+0x324/0x3e0 kernel/locking/lockdep.c:1827 check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x29bb/0x5570 kernel/locking/lockdep.c:4426 lock_acquire+0x1f3/0xae0 kernel/locking/lockdep.c:5006 flush_workqueue+0x110/0x13e0 kernel/workqueue.c:2780 flush_scheduled_work include/linux/workqueue.h:597 [inline] tipc_exit_net+0x47/0x2a0 net/tipc/core.c:116 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:186 cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:603 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 tipc: TX() has been purged, node left! tipc: TX() has been purged, node left!