[syzbot] [bluetooth?] possible deadlock in hci_unregister_dev (2)

[syzbot] [bluetooth?] possible deadlock in hci_unregister_dev (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    bb7a2467e6be Add linux-next specific files for 20240426
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13daed0f180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6a0288262dd108
dashboard link: https://syzkaller.appspot.com/bug?extid=ab10eccaaf6fdf23dd55
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5175af7dda64/disk-bb7a2467.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70db0462e868/vmlinux-bb7a2467.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3217fb825698/bzImage-bb7a2467.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ab10eccaaf6fdf23dd55@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc5-next-20240426-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/6085 is trying to acquire lock:
ffff8880696fc8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
ffff8880696fc8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
ffff8880696fc8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4113 [inline]
ffff8880696fc8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: __flush_work+0xe6/0xd00 kernel/workqueue.c:4172

but task is already holding lock:
ffff8880696fd060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:559 [inline]
ffff8880696fd060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x1d3/0x4e0 net/bluetooth/hci_core.c:2778

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->req_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:309
       process_one_work kernel/workqueue.c:3222 [inline]
       process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3303
       worker_thread+0x86d/0xd70 kernel/workqueue.c:3384
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       touch_work_lockdep_map kernel/workqueue.c:3885 [inline]
       start_flush_work kernel/workqueue.c:4139 [inline]
       __flush_work+0x73c/0xd00 kernel/workqueue.c:4172
       __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4322
       hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:588
       hci_dev_close_sync+0xbae/0x1060 net/bluetooth/hci_sync.c:5188
       hci_dev_do_close net/bluetooth/hci_core.c:561 [inline]
       hci_unregister_dev+0x1db/0x4e0 net/bluetooth/hci_core.c:2778
       vhci_release+0x83/0xd0 drivers/bluetooth/hci_vhci.c:674
       __fput+0x406/0x8b0 fs/file_table.c:422
       task_work_run+0x24f/0x310 kernel/task_work.c:180
       exit_task_work include/linux/task_work.h:38 [inline]
       do_exit+0xa27/0x27e0 kernel/exit.c:874
       do_group_exit+0x207/0x2c0 kernel/exit.c:1023
       __do_sys_exit_group kernel/exit.c:1034 [inline]
       __se_sys_exit_group kernel/exit.c:1032 [inline]
       __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1032
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&hdev->req_lock);
                               lock((work_completion)(&hdev->cmd_sync_work));
                               lock(&hdev->req_lock);
  lock((work_completion)(&hdev->cmd_sync_work));

 *** DEADLOCK ***

2 locks held by syz-executor.0/6085:
 #0: ffff8880696fd060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:559 [inline]
 #0: ffff8880696fd060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x1d3/0x4e0 net/bluetooth/hci_core.c:2778
 #1: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #1: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #1: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: start_flush_work kernel/workqueue.c:4113 [inline]
 #1: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: __flush_work+0xe6/0xd00 kernel/workqueue.c:4172

stack backtrace:
CPU: 0 PID: 6085 Comm: syz-executor.0 Not tainted 6.9.0-rc5-next-20240426-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
 touch_work_lockdep_map kernel/workqueue.c:3885 [inline]
 start_flush_work kernel/workqueue.c:4139 [inline]
 __flush_work+0x73c/0xd00 kernel/workqueue.c:4172
 __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4322
 hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:588
 hci_dev_close_sync+0xbae/0x1060 net/bluetooth/hci_sync.c:5188
 hci_dev_do_close net/bluetooth/hci_core.c:561 [inline]
 hci_unregister_dev+0x1db/0x4e0 net/bluetooth/hci_core.c:2778
 vhci_release+0x83/0xd0 drivers/bluetooth/hci_vhci.c:674
 __fput+0x406/0x8b0 fs/file_table.c:422
 task_work_run+0x24f/0x310 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0xa27/0x27e0 kernel/exit.c:874
 do_group_exit+0x207/0x2c0 kernel/exit.c:1023
 __do_sys_exit_group kernel/exit.c:1034 [inline]
 __se_sys_exit_group kernel/exit.c:1032 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1032
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1eb1a7dea9
Code: Unable to access opcode bytes at 0x7f1eb1a7de7f.
RSP: 002b:00007ffdd8d72208 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f1eb1ac93de RCX: 00007f1eb1a7dea9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000002 R08: 00007ffdd8d6ffa7 R09: 00007ffdd8d734c0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdd8d734c0
R13: 00007f1eb1ac93b9 R14: 000000000001e31b R15: 0000000000000003
 </TASK>


---
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