FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 1
CPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 fail_dump lib/fault-inject.c:73 [inline]
 should_fail_ex+0x412/0x560 lib/fault-inject.c:174
 should_failslab+0xa8/0x100 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4454 [inline]
 slab_alloc_node mm/slub.c:4807 [inline]
 __do_kmalloc_node mm/slub.c:5218 [inline]
 __kmalloc_noprof+0xe8/0x760 mm/slub.c:5231
 kmalloc_noprof include/linux/slab.h:966 [inline]
 kzalloc_noprof include/linux/slab.h:1200 [inline]
 kobject_get_path+0xc5/0x2f0 lib/kobject.c:161
 kobject_uevent_env+0x2a1/0x9e0 lib/kobject_uevent.c:545
 device_del+0x750/0x8f0 drivers/base/core.c:3896
 cdev_device_del+0x27/0xf0 fs/char_dev.c:577
 evdev_disconnect+0x4c/0xb0 drivers/input/evdev.c:1403
 __input_unregister_device+0x3a3/0x640 drivers/input/input.c:2189
 input_unregister_device+0x9b/0x100 drivers/input/input.c:2418
 hidp_session_dev_del net/bluetooth/hidp/core.c:876 [inline]
 hidp_session_remove+0x135/0x260 net/bluetooth/hidp/core.c:1172
 l2cap_unregister_all_users net/bluetooth/l2cap_core.c:1741 [inline]
 l2cap_conn_del+0x249/0x5c0 net/bluetooth/l2cap_core.c:1772
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline]
 hci_conn_hash_flush+0x10d/0x260 net/bluetooth/hci_conn.c:2644
 hci_dev_close_sync+0x821/0x10e0 net/bluetooth/hci_sync.c:5358
 hci_dev_do_close net/bluetooth/hci_core.c:502 [inline]
 hci_dev_close+0x108/0x260 net/bluetooth/hci_core.c:527
 sock_do_ioctl+0x101/0x320 net/socket.c:1254
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa7d159c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa7d246f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa7d1816090 RCX: 00007fa7d159c799
RDX: 0000000000000000 RSI: 00000000400448ca RDI: 0000000000000006
RBP: 00007fa7d246f090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fa7d1816128 R14: 00007fa7d1816090 R15: 00007ffeb404faa8
 </TASK>
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.0/5318 is trying to acquire lock:
ffff8880124dc840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
ffff8880124dc840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
ffff8880124dc840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4233 [inline]
ffff8880124dc840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0x100/0xc50 kernel/workqueue.c:4291

but task is already holding lock:
ffff8880124dcaf8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x7b/0x5c0 net/bluetooth/l2cap_core.c:1755

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock#2){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
       l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1661
       process_one_work kernel/workqueue.c:3275 [inline]
       process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
       worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
       kthread+0x388/0x470 kernel/kthread.c:467
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
       touch_work_lockdep_map kernel/workqueue.c:4005 [inline]
       start_flush_work kernel/workqueue.c:4259 [inline]
       __flush_work+0x700/0xc50 kernel/workqueue.c:4291
       __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4447
       l2cap_conn_del+0x40f/0x5c0 net/bluetooth/l2cap_core.c:1791
       hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline]
       hci_conn_hash_flush+0x10d/0x260 net/bluetooth/hci_conn.c:2644
       hci_dev_close_sync+0x821/0x10e0 net/bluetooth/hci_sync.c:5358
       hci_dev_do_close net/bluetooth/hci_core.c:502 [inline]
       hci_dev_close+0x108/0x260 net/bluetooth/hci_core.c:527
       sock_do_ioctl+0x101/0x320 net/socket.c:1254
       sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&conn->lock#2);
                               lock((work_completion)(&(&conn->info_timer)->work));
                               lock(&conn->lock#2);
  lock((work_completion)(&(&conn->info_timer)->work));

 *** DEADLOCK ***

5 locks held by syz.0.0/5318:
 #0: ffff888038678ec0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close net/bluetooth/hci_core.c:500 [inline]
 #0: ffff888038678ec0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_close+0x100/0x260 net/bluetooth/hci_core.c:527
 #1: ffff8880386780c0 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x640/0x10e0 net/bluetooth/hci_sync.c:5346
 #2: ffffffff8fd5b3e8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2151 [inline]
 #2: ffffffff8fd5b3e8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xa1/0x260 net/bluetooth/hci_conn.c:2644
 #3: ffff8880124dcaf8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x7b/0x5c0 net/bluetooth/l2cap_core.c:1755
 #4: ffffffff8e7602e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #4: ffffffff8e7602e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #4: ffffffff8e7602e0 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4233 [inline]
 #4: ffffffff8e7602e0 (rcu_read_lock){....}-{1:3}, at: __flush_work+0x100/0xc50 kernel/workqueue.c:4291

stack backtrace:
CPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 touch_work_lockdep_map kernel/workqueue.c:4005 [inline]
 start_flush_work kernel/workqueue.c:4259 [inline]
 __flush_work+0x700/0xc50 kernel/workqueue.c:4291
 __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4447
 l2cap_conn_del+0x40f/0x5c0 net/bluetooth/l2cap_core.c:1791
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline]
 hci_conn_hash_flush+0x10d/0x260 net/bluetooth/hci_conn.c:2644
 hci_dev_close_sync+0x821/0x10e0 net/bluetooth/hci_sync.c:5358
 hci_dev_do_close net/bluetooth/hci_core.c:502 [inline]
 hci_dev_close+0x108/0x260 net/bluetooth/hci_core.c:527
 sock_do_ioctl+0x101/0x320 net/socket.c:1254
 sock_ioctl+0x5c6/0x7f0 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa7d159c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa7d246f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa7d1816090 RCX: 00007fa7d159c799
RDX: 0000000000000000 RSI: 00000000400448ca RDI: 0000000000000006
RBP: 00007fa7d246f090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fa7d1816128 R14: 00007fa7d1816090 R15: 00007ffeb404faa8
 </TASK>