[v6.1] possible deadlock in hci_conn_hash_flush

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 543aff194ab6 Linux 6.1.23
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=176f5bf7c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9affea290775ea7
dashboard link: https://syzkaller.appspot.com/bug?extid=def4b0d43f4bb081dcc5
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/6fe9097a8f09/disk-543aff19.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9df5aa0f6266/vmlinux-543aff19.xz
kernel image: https://storage.googleapis.com/syzbot-assets/84127c4bde2b/bzImage-543aff19.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+def4b0...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.23-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/14113 is trying to acquire lock:
ffff88807830cc70 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: __flush_work+0xcf/0x1a0 kernel/workqueue.c:3069

but task is already holding lock:
ffffffff8e1e15e8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1789 [inline]
ffffffff8e1e15e8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xb8/0x210 net/bluetooth/hci_conn.c:2440

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (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:1774 [inline]
hci_remote_features_evt+0x671/0xaa0 net/bluetooth/hci_event.c:3758
hci_event_func net/bluetooth/hci_event.c:7475 [inline]
hci_event_packet+0x96c/0x1360 net/bluetooth/hci_event.c:7527
hci_rx_work+0x40d/0xa80 net/bluetooth/hci_core.c:4058
process_one_work+0x8aa/0x11f0 kernel/workqueue.c:2289
worker_thread+0xa5f/0x1210 kernel/workqueue.c:2436
kthread+0x268/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #2 (&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

-> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
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:1721 [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+0x268/0x300 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #0 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{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
__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:1792 [inline]
hci_conn_hash_flush+0x10d/0x210 net/bluetooth/hci_conn.c:2440
hci_dev_close_sync+0xa2d/0x1000 net/bluetooth/hci_sync.c:4875
hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
hci_unregister_dev+0x1c6/0x470 net/bluetooth/hci_core.c:2702
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
__do_sys_exit_group kernel/exit.c:1030 [inline]
__se_sys_exit_group kernel/exit.c:1028 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1028
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

other info that might help us debug this:

Chain exists of:
(work_completion)(&(&conn->timeout_work)->work) --> &hdev->lock --> hci_cb_list_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(hci_cb_list_lock);
lock(&hdev->lock);
lock(hci_cb_list_lock);
lock((work_completion)(&(&conn->timeout_work)->work));

*** DEADLOCK ***

3 locks held by syz-executor.4/14113:
#0: ffff888077e25028 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close net/bluetooth/hci_core.c:552 [inline]
#0: ffff888077e25028 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x1be/0x470 net/bluetooth/hci_core.c:2702
#1: ffff888077e24078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x445/0x1000 net/bluetooth/hci_sync.c:4862
#2: ffffffff8e1e15e8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1789 [inline]
#2: ffffffff8e1e15e8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xb8/0x210 net/bluetooth/hci_conn.c:2440

stack backtrace:
CPU: 1 PID: 14113 Comm: syz-executor.4 Not tainted 6.1.23-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
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
__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:1792 [inline]
hci_conn_hash_flush+0x10d/0x210 net/bluetooth/hci_conn.c:2440
hci_dev_close_sync+0xa2d/0x1000 net/bluetooth/hci_sync.c:4875
hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
hci_unregister_dev+0x1c6/0x470 net/bluetooth/hci_core.c:2702
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
__do_sys_exit_group kernel/exit.c:1030 [inline]
__se_sys_exit_group kernel/exit.c:1028 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1028
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
RIP: 0033:0x7f972428c169
Code: Unable to access opcode bytes at 0x7f972428c13f.
RSP: 002b:00007fff6f8bc908 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fff6f8bcab0 RCX: 00007f972428c169
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000043
RBP: 0000000000000000 R08: 0000000000000025 R09: 00007fff6f8bcab0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f97242e7c72
R13: 000000000000001c R14: 0000000000000016 R15: 00007fff6f8bcaf0
</TASK>


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[syzbot]

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