[v6.1] possible deadlock in sco_sock_timeout

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e84a4e368abe Linux 6.1.35
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=137f8277280000
kernel config: https://syzkaller.appspot.com/x/.config?x=a69b5c9de715622a
dashboard link: https://syzkaller.appspot.com/bug?extid=29896aa9c2933bc6375d
compiler: Debian clang version 15.0.7, 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/3c7fedd1a86d/disk-e84a4e36.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8b34c6296ed7/vmlinux-e84a4e36.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a88164798cc2/bzImage-e84a4e36.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+29896a...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.35-syzkaller #0 Not tainted
------------------------------------------------------
kworker/0:3/3648 is trying to acquire lock:
ffff888017ecd130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1733 [inline]
ffff888017ecd130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_sock_timeout+0xbd/0x230 net/bluetooth/sco.c:97

but task is already holding lock:
ffffc9000409fd20 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__flush_work+0xeb/0x1a0 kernel/workqueue.c:3069
__cancel_work_timer+0x519/0x6a0 kernel/workqueue.c:3160
sco_conn_del+0x205/0x300 net/bluetooth/sco.c:205
hci_disconn_cfm include/net/bluetooth/hci_core.h:1794 [inline]
hci_conn_hash_flush+0x10e/0x280 net/bluetooth/hci_conn.c:2457
hci_dev_close_sync+0xa2d/0x1000 net/bluetooth/hci_sync.c:4891
hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
hci_unregister_dev+0x1df/0x480 net/bluetooth/hci_core.c:2704
vhci_release+0x7f/0xd0 drivers/bluetooth/hci_vhci.c:568
__fput+0x3b7/0x890 fs/file_table.c:320
task_work_run+0x246/0x300 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x6fb/0x2300 kernel/exit.c:869
do_group_exit+0x202/0x2b0 kernel/exit.c:1019
get_signal+0x16f7/0x17d0 kernel/signal.c:2858
arch_do_signal_or_restart+0xb0/0x1a10 arch/x86/kernel/signal.c:869
exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:297
ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:299

-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
hci_connect_cfm include/net/bluetooth/hci_core.h:1776 [inline]
hci_remote_features_evt+0x671/0xaa0 net/bluetooth/hci_event.c:3753
hci_event_func net/bluetooth/hci_event.c:7476 [inline]
hci_event_packet+0x96c/0x1360 net/bluetooth/hci_event.c:7528
hci_rx_work+0x40d/0xa80 net/bluetooth/hci_core.c:4060
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #1 (&hdev->lock){+.+.}-{3:3}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
__mutex_lock_common+0x1d4/0x2520 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
sco_sock_connect+0x181/0x8d0 net/bluetooth/sco.c:593
__sys_connect_file net/socket.c:1976 [inline]
__sys_connect+0x2c9/0x300 net/socket.c:1993
__do_sys_connect net/socket.c:2003 [inline]
__se_sys_connect net/socket.c:2000 [inline]
__x64_sys_connect+0x76/0x80 net/socket.c:2000
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
lock_sock_nested+0x44/0x100 net/core/sock.c:3458
lock_sock include/net/sock.h:1733 [inline]
sco_sock_timeout+0xbd/0x230 net/bluetooth/sco.c:97
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

other info that might help us debug this:

Chain exists of:
sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> hci_cb_list_lock --> (work_completion)(&(&conn->timeout_work)->work)

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock((work_completion)(&(&conn->timeout_work)->work));
lock(hci_cb_list_lock);
lock((work_completion)(&(&conn->timeout_work)->work));
lock(sk_lock-AF_BLUETOOTH-BTPROTO_SCO);

*** DEADLOCK ***

2 locks held by kworker/0:3/3648:
#0: ffff888012464d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x77a/0x11f0
#1: ffffc9000409fd20 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7bd/0x11f0 kernel/workqueue.c:2264

stack backtrace:
CPU: 0 PID: 3648 Comm: kworker/0:3 Not tainted 6.1.35-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Workqueue: events sco_sock_timeout
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3098 [inline]
check_prevs_add kernel/locking/lockdep.c:3217 [inline]
validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
lock_sock_nested+0x44/0x100 net/core/sock.c:3458
lock_sock include/net/sock.h:1733 [inline]
sco_sock_timeout+0xbd/0x230 net/bluetooth/sco.c:97
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x26e/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.