Re: [syzbot] [ocfs2?] WARNING in ocfs2_unlink

[syzbot <syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in l2cap_conn_del

(syz-executor,6305,1):ocfs2_read_locked_inode:597 ERROR: status = -117
(syz-executor,6305,1):ocfs2_validate_inode_block:1465 ERROR: Invalid dinode #17057: i_mode is zero!
(syz-executor,6305,1):ocfs2_read_locked_inode:597 ERROR: status = -117
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor/6305 is trying to acquire lock:
ffff88802ed7c040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
ffff88802ed7c040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
ffff88802ed7c040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4179 [inline]
ffff88802ed7c040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0xd2/0xbc0 kernel/workqueue.c:4237

but task is already holding lock:
ffff88802ed7c338 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680 net/bluetooth/l2cap_core.c:1762

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock#2){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x17d/0x12e0 kernel/locking/mutex.c:760
       l2cap_info_timeout+0x60/0xa0 net/bluetooth/l2cap_core.c:1668
       process_one_work kernel/workqueue.c:3263 [inline]
       process_scheduled_works+0xa55/0x16b0 kernel/workqueue.c:3346
       worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       touch_work_lockdep_map kernel/workqueue.c:3951 [inline]
       start_flush_work kernel/workqueue.c:4205 [inline]
       __flush_work+0x6b8/0xbc0 kernel/workqueue.c:4237
       __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4393
       l2cap_conn_del+0x4f0/0x680 net/bluetooth/l2cap_core.c:1796
       hci_disconn_cfm include/net/bluetooth/hci_core.h:2121 [inline]
       hci_conn_hash_flush+0x10d/0x230 net/bluetooth/hci_conn.c:2602
       hci_dev_close_sync+0xa0a/0x11b0 net/bluetooth/hci_sync.c:5303
       hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
       hci_unregister_dev+0x21a/0x510 net/bluetooth/hci_core.c:2715
       vhci_release+0x152/0x1a0 drivers/bluetooth/hci_vhci.c:690
       __fput+0x44c/0xa70 fs/file_table.c:468
       task_work_run+0x1d4/0x260 kernel/task_work.c:227
       exit_task_work include/linux/task_work.h:40 [inline]
       do_exit+0x6b5/0x2300 kernel/exit.c:966
       do_group_exit+0x21c/0x2d0 kernel/exit.c:1107
       __do_sys_exit_group kernel/exit.c:1118 [inline]
       __se_sys_exit_group kernel/exit.c:1116 [inline]
       __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1116
       x64_sys_call+0x21f7/0x2200 arch/x86/include/generated/asm/syscalls_64.h:232
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&conn->lock#2);
                               lock((work_completion)(&(&conn->info_timer)->work));
                               lock(&conn->lock#2);
  lock((work_completion)(&(&conn->info_timer)->work));

 *** DEADLOCK ***

5 locks held by syz-executor/6305:
 #0: ffff888026654dc8 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close net/bluetooth/hci_core.c:499 [inline]
 #0: ffff888026654dc8 (&hdev->req_lock){+.+.}-{4:4}, at: hci_unregister_dev+0x212/0x510 net/bluetooth/hci_core.c:2715
 #1: ffff8880266540b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x5b3/0x11b0 net/bluetooth/hci_sync.c:5291
 #2: ffffffff8f1f8ca8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2118 [inline]
 #2: ffffffff8f1f8ca8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xa1/0x230 net/bluetooth/hci_conn.c:2602
 #3: ffff88802ed7c338 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680 net/bluetooth/l2cap_core.c:1762
 #4: ffffffff8dd3cc20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #4: ffffffff8dd3cc20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #4: ffffffff8dd3cc20 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4179 [inline]
 #4: ffffffff8dd3cc20 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xd2/0xbc0 kernel/workqueue.c:4237

stack backtrace:
CPU: 0 UID: 0 PID: 6305 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 touch_work_lockdep_map kernel/workqueue.c:3951 [inline]
 start_flush_work kernel/workqueue.c:4205 [inline]
 __flush_work+0x6b8/0xbc0 kernel/workqueue.c:4237
 __cancel_work_sync+0xbe/0x110 kernel/workqueue.c:4393
 l2cap_conn_del+0x4f0/0x680 net/bluetooth/l2cap_core.c:1796
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2121 [inline]
 hci_conn_hash_flush+0x10d/0x230 net/bluetooth/hci_conn.c:2602
 hci_dev_close_sync+0xa0a/0x11b0 net/bluetooth/hci_sync.c:5303
 hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
 hci_unregister_dev+0x21a/0x510 net/bluetooth/hci_core.c:2715
 vhci_release+0x152/0x1a0 drivers/bluetooth/hci_vhci.c:690
 __fput+0x44c/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x6b5/0x2300 kernel/exit.c:966
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1107
 __do_sys_exit_group kernel/exit.c:1118 [inline]
 __se_sys_exit_group kernel/exit.c:1116 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1116
 x64_sys_call+0x21f7/0x2200 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7814385d29
Code: Unable to access opcode bytes at 0x7f7814385cff.
RSP: 002b:00007ffc212d6318 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f7814401919 RCX: 00007f7814385d29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 000000000000000d R08: 00007ffc212d40b6 R09: 00007ffc212d75d0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc212d75d0
R13: 00007f78144018f4 R14: 00007ffc212d8690 R15: 0000000000000001
 </TASK>


Tested on:

commit:         6fab32bb MAINTAINERS: add Mark Brown as a linux-next m..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178fb734580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1215729170d20fc
dashboard link: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1361c614580000