possible deadlock in vmci_qp_broker

possible deadlock in vmci_qp_broker_detach
Status: upstream: reported syz repro on 2021/03/26 01:19
Reported-by: syzbot+44e40ac2cfe68e8ce207@syzkaller.appspotmail.com
First crash: 32d, last: 8d14h

Cause bisection: introduced by (bisect log) [no-op commit]:
commit 2dd209f00fc5a1caafa493066c7cd692fd2fd57c
Author: Bart Van Assche <bvanassche@acm.org>
Date: Tue Mar 10 04:26:16 2020 +0000

blk-mq: Fix a comment in include/linux/blk-mq.h

Crash: possible deadlock in vmci_qp_broker_detach (log)
Repro: syz .config

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.19	possible deadlock in vmci_qp_broker_detach	C			3	10d	115d	0/1	upstream: reported C repro on 2020/12/28 17:12

Sample crash report:

============================================
WARNING: possible recursive locking detected
5.12.0-rc7-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.0/9888 is trying to acquire lock:
ffffffff8ca64958 (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:
ffffffff8ca64958 (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.0/9888:
 #0: ffffffff8ca64958 (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: 1 PID: 9888 Comm: syz-executor.0 Not tainted 5.12.0-rc7-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:2830 [inline]
 check_deadlock kernel/locking/lockdep.c:2873 [inline]
 validate_chain kernel/locking/lockdep.c:3662 [inline]
 __lock_acquire.cold+0x14c/0x3b4 kernel/locking/lockdep.c:4901
 lock_acquire kernel/locking/lockdep.c:5511 [inline]
 lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5476
 __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: 0033:0x466459
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f286b9f9188 EFLAGS: 00000246 ORIG_RAX: 0000000000000124
RAX: 0000000000000003 RBX: 000000000056bf60 RCX: 0000000000466459
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 0000000000a9fb1f R14: 00007f286b9f9300 R15: 0000000000022000

Crashes (6):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	VM info	Title
ci-upstream-kasan-gce	2021/04/14 15:29	upstream	50987bec	3134b37f	.config	log	report	syz		possible deadlock in vmci_qp_broker_detach
ci-upstream-kasan-gce-smack-root	2021/04/12 17:28	upstream	d434405a	bfeda1b1	.config	log	report	syz		possible deadlock in vmci_qp_broker_detach
ci-upstream-kasan-gce	2021/04/14 11:37	upstream	50987bec	3134b37f	.config	log	report		info	possible deadlock in vmci_qp_broker_detach
ci-upstream-kasan-gce-smack-root	2021/04/12 16:01	upstream	d434405a	bfeda1b1	.config	log	report		info	possible deadlock in vmci_qp_broker_detach
ci-upstream-kasan-gce	2021/03/31 10:37	upstream	2bb25b3a	6a81331a	.config	log	report		info	possible deadlock in vmci_qp_broker_detach
ci-upstream-kasan-gce	2021/03/22 01:14	upstream	5ee96fa9	bea32f74	.config	log	report		info	possible deadlock in vmci_qp_broker_detach