[v5.15] possible deadlock in vmci_qp_broker_detach (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 241d66fa280c Linux 5.15.208
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1340b17e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=9a38a001766aeb35e4d4
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d3e9d10633a1/disk-241d66fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/beca1f713e4b/vmlinux-241d66fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/26a15a6e1c14/bzImage-241d66fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9a38a0...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.2.399/6204 is trying to acquire lock:
ffffffff8cb41a58 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x113/0x10f0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2095

but task is already holding lock:
ffffffff8cb41a58 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x113/0x10f0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2095

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.2.399/6204:
#0: ffffffff8cb41a58 (qp_broker_list.mutex){+.+.}-{3:3}, at: vmci_qp_broker_detach+0x113/0x10f0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2095

stack backtrace:
CPU: 1 PID: 6204 Comm: syz.2.399 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
__lock_acquire+0x1236/0x7d10 kernel/locking/lockdep.c:-1
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1e3/0x2400 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
vmci_qp_broker_detach+0x113/0x10f0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2095
ctx_free_ctx drivers/misc/vmw_vmci/vmci_context.c:444 [inline]
kref_put include/linux/kref.h:65 [inline]
vmci_ctx_put+0x5e4/0xc00 drivers/misc/vmw_vmci/vmci_context.c:497
vmci_ctx_enqueue_datagram+0x3a7/0x420 drivers/misc/vmw_vmci/vmci_context.c:360
dg_dispatch_as_host drivers/misc/vmw_vmci/vmci_datagram.c:276 [inline]
vmci_datagram_dispatch+0x449/0xc20 drivers/misc/vmw_vmci/vmci_datagram.c:340
qp_notify_peer drivers/misc/vmw_vmci/vmci_queue_pair.c:1481 [inline]
vmci_qp_broker_detach+0xab4/0x10f0 drivers/misc/vmw_vmci/vmci_queue_pair.c:2188
ctx_free_ctx drivers/misc/vmw_vmci/vmci_context.c:444 [inline]
kref_put include/linux/kref.h:65 [inline]
vmci_ctx_put+0x5e4/0xc00 drivers/misc/vmw_vmci/vmci_context.c:497
vmci_host_close+0x97/0x160 drivers/misc/vmw_vmci/vmci_host.c:143
__fput+0x234/0x930 fs/file_table.c:311
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdb3d10de59
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:00007fdb3b346028 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fdb3d387090 RCX: 00007fdb3d10de59
RDX: 0000000000000000 RSI: ffffffffffffffff RDI: 0000000000000007
RBP: 00007fdb3d1a3d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb3d387128 R14: 00007fdb3d387090 R15: 00007ffdb789ade8
</TASK>


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