[syzbot] possible deadlock in vmci_qp_broker_detach

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    5ee96fa9 Merge tag 'irq-urgent-2021-03-21' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15466edcd00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6abda3336c698a07
dashboard link: https://syzkaller.appspot.com/bug?extid=44e40ac2cfe68e8ce207

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+44e40ac2cfe68e8ce207@xxxxxxxxxxxxxxxxxxxxxxxxx

============================================
WARNING: possible recursive locking detected
5.12.0-rc3-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.2/24589 is trying to acquire lock:
ffffffff8ca63f38 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x147/0x11b0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2093

but task is already holding lock:
ffffffff8ca63f38 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x147/0x11b0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2093

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(qp_broker_list.mutex);
  lock(qp_broker_list.mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor.2/24589:
 #0: ffffffff8ca63f38 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x147/0x11b0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2093

stack backtrace:
CPU: 0 PID: 24589 Comm: syz-executor.2 Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 print_deadlock_bug kernel/locking/lockdep.c:2829 [inline]
 check_deadlock kernel/locking/lockdep.c:2872 [inline]
 validate_chain kernel/locking/lockdep.c:3661 [inline]
 __lock_acquire.cold+0x14c/0x3b4 kernel/locking/lockdep.c:4900
 lock_acquire kernel/locking/lockdep.c:5510 [inline]
 lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5475
 __mutex_lock_common kernel/locking/mutex.c:949 [inline]
 __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096
 vmci_qp_broker_detach+0x147/0x11b0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2093
 ctx_free_ctx+0x4e5/0xd30 drivers/misc/vmw_vmci/vmci_context.c:444
 kref_put include/linux/kref.h:65 [inline]
 vmci_ctx_put drivers/misc/vmw_vmci/vmci_context.c:497 [inline]
 vmci_ctx_enqueue_datagram+0x4dc/0x620 drivers/misc/vmw_vmci/vmci_context.c:360
 dg_dispatch_as_host drivers/misc/vmw_vmci/vmci_datagram.c:275 [inline]
 vmci_datagram_dispatch+0x39b/0xb50 drivers/misc/vmw_vmci/vmci_datagram.c:339
 qp_notify_peer+0x182/0x260 drivers/misc/vmw_vmci/vmci_queue_pair.c:1479
 vmci_qp_broker_detach+0xa09/0x11b0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2186
 ctx_free_ctx+0x4e5/0xd30 drivers/misc/vmw_vmci/vmci_context.c:444
 kref_put include/linux/kref.h:65 [inline]
 vmci_ctx_put drivers/misc/vmw_vmci/vmci_context.c:497 [inline]
 vmci_ctx_destroy+0x169/0x1d0 drivers/misc/vmw_vmci/vmci_context.c:195
 vmci_host_close+0x116/0x1a0 drivers/misc/vmw_vmci/vmci_host.c:143
 __fput+0x288/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x41926b
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
RSP: 002b:0000000000a9fb80 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 000000000041926b
RDX: 0000001b32f25054 RSI: 0000001b32f24cec RDI: 0000000000000004
RBP: 0000000000000001 R08: 0000000000000000 R09: 000000000000165e
R10: 000000008afb7662 R11: 0000000000000293 R12: 000000000056c9e0
R13: 000000000056c9e0 R14: 000000000056bf60 R15: 0000000000212216


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