linux-kernel - [syzbot] possible deadlock in discov

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Message-ID: <0000000000000b46aa05ea1c2721@google.com>
Date:   Mon, 03 Oct 2022 00:18:38 -0700
From:   syzbot <syzbot+f047480b1e906b46a3f4@...kaller.appspotmail.com>
To:     davem@...emloft.net, edumazet@...gle.com, johan.hedberg@...il.com,
        kuba@...nel.org, linux-bluetooth@...r.kernel.org,
        linux-kernel@...r.kernel.org, luiz.dentz@...il.com,
        marcel@...tmann.org, netdev@...r.kernel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: [syzbot] possible deadlock in discov_off

Hello,

syzbot found the following issue on:

HEAD commit:    c3e0e1e23c70 Merge tag 'irq_urgent_for_v6.0' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14471d38880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=755695d26ad09807
dashboard link: https://syzkaller.appspot.com/bug?extid=f047480b1e906b46a3f4
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/67576e43d5c7/disk-c3e0e1e2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e568fb42b955/vmlinux-c3e0e1e2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f047480b1e906b46a3f4@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc7-syzkaller-00081-gc3e0e1e23c70 #0 Not tainted
------------------------------------------------------
kworker/u5:5/3650 is trying to acquire lock:
ffff88807606c078 (&hdev->lock){+.+.}-{3:3}, at: discov_off+0x88/0x1a0 net/bluetooth/mgmt.c:1033

but task is already holding lock:
ffffc90003f5fda8 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}:
       __flush_work+0x105/0xae0 kernel/workqueue.c:3069
       __cancel_work_timer+0x3f9/0x570 kernel/workqueue.c:3160
       mgmt_index_removed+0x218/0x340 net/bluetooth/mgmt.c:8952
       hci_unregister_dev+0x34f/0x4e0 net/bluetooth/hci_core.c:2688
       vhci_release+0x7c/0xf0 drivers/bluetooth/hci_vhci.c:568
       __fput+0x277/0x9d0 fs/file_table.c:320
       task_work_run+0xdd/0x1a0 kernel/task_work.c:177
       exit_task_work include/linux/task_work.h:38 [inline]
       do_exit+0xad5/0x29b0 kernel/exit.c:795
       do_group_exit+0xd2/0x2f0 kernel/exit.c:925
       get_signal+0x238c/0x2610 kernel/signal.c:2857
       arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
       exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
       exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
       __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
       syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
       do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&hdev->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3829 [inline]
       __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
       lock_acquire kernel/locking/lockdep.c:5666 [inline]
       lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
       discov_off+0x88/0x1a0 net/bluetooth/mgmt.c:1033
       process_one_work+0x991/0x1610 kernel/workqueue.c:2289
       worker_thread+0x665/0x1080 kernel/workqueue.c:2436
       kthread+0x2e4/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((work_completion)(&(&hdev->discov_off)->work));
                               lock(&hdev->lock);
                               lock((work_completion)(&(&hdev->discov_off)->work));
  lock(&hdev->lock);

 *** DEADLOCK ***

2 locks held by kworker/u5:5/3650:
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline]
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline]
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:636 [inline]
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:663 [inline]
 #0: ffff88807a95e938 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x87a/0x1610 kernel/workqueue.c:2260
 #1: ffffc90003f5fda8 ((work_completion)(&(&hdev->discov_off)->work)){+.+.}-{0:0}, at: process_one_work+0x8ae/0x1610 kernel/workqueue.c:2264

stack backtrace:
CPU: 0 PID: 3650 Comm: kworker/u5:5 Not tainted 6.0.0-rc7-syzkaller-00081-gc3e0e1e23c70 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Workqueue: hci0 discov_off
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3829 [inline]
 __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053
 lock_acquire kernel/locking/lockdep.c:5666 [inline]
 lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
 discov_off+0x88/0x1a0 net/bluetooth/mgmt.c:1033
 process_one_work+0x991/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>


---
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