Re: [syzbot] [bluetooth?] BUG: corrupted list in hci_chan_del (2)

[syzbot <syzbot+10bd8fe6741eedd2be2e@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in l2cap_sock_shutdown

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc1-next-20250207-syzkaller-02219-ged58d103e6da-dirty #0 Not tainted
------------------------------------------------------
syz.0.16/6578 is trying to acquire lock:
ffff888012844078 (&hdev->lock){+.+.}-{4:4}, at: l2cap_sock_shutdown+0xa41/0x10c0 net/bluetooth/l2cap_sock.c:1363

but task is already holding lock:
ffff888079163518 (&chan->lock/1){+.+.}-{4:4}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
ffff888079163518 (&chan->lock/1){+.+.}-{4:4}, at: l2cap_sock_shutdown+0x9c9/0x10c0 net/bluetooth/l2cap_sock.c:1360

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&chan->lock/1){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       l2cap_chan_connect+0x7e7/0xeb0 net/bluetooth/l2cap_core.c:7084
       l2cap_sock_connect+0x5c9/0x800 net/bluetooth/l2cap_sock.c:256
       __sys_connect_file net/socket.c:2045 [inline]
       __sys_connect+0x288/0x2d0 net/socket.c:2064
       __do_sys_connect net/socket.c:2070 [inline]
       __se_sys_connect net/socket.c:2067 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2067
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&conn->chan_lock){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       l2cap_conn_ready net/bluetooth/l2cap_core.c:1627 [inline]
       l2cap_connect_cfm+0x5b4/0x1090 net/bluetooth/l2cap_core.c:7288
       hci_connect_cfm include/net/bluetooth/hci_core.h:2051 [inline]
       hci_remote_features_evt+0x68e/0xac0 net/bluetooth/hci_event.c:3726
       hci_event_func net/bluetooth/hci_event.c:7473 [inline]
       hci_event_packet+0xac2/0x1540 net/bluetooth/hci_event.c:7525
       hci_rx_work+0x3f3/0xdb0 net/bluetooth/hci_core.c:4015
       process_one_work kernel/workqueue.c:3236 [inline]
       process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
       worker_thread+0x870/0xd30 kernel/workqueue.c:3398
       kthread+0x7a9/0x920 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (&hdev->lock){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       l2cap_sock_shutdown+0xa41/0x10c0 net/bluetooth/l2cap_sock.c:1363
       l2cap_sock_release+0x79/0x1d0 net/bluetooth/l2cap_sock.c:1419
       __sock_release net/socket.c:647 [inline]
       sock_close+0xbc/0x240 net/socket.c:1398
       __fput+0x3e9/0x9f0 fs/file_table.c:464
       task_work_run+0x24f/0x310 kernel/task_work.c:227
       get_signal+0x15f7/0x1750 kernel/signal.c:2809
       arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
       exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
       exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
       __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
       syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
       do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &hdev->lock --> &conn->chan_lock --> &chan->lock/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&chan->lock/1);
                               lock(&conn->chan_lock);
                               lock(&chan->lock/1);
  lock(&hdev->lock);

 *** DEADLOCK ***

2 locks held by syz.0.16/6578:
 #0: ffff888079a38e08 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline]
 #0: ffff888079a38e08 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: __sock_release net/socket.c:646 [inline]
 #0: ffff888079a38e08 (&sb->s_type->i_mutex_key#10){+.+.}-{4:4}, at: sock_close+0x90/0x240 net/socket.c:1398
 #1: ffff888079163518 (&chan->lock/1){+.+.}-{4:4}, at: l2cap_chan_lock include/net/bluetooth/l2cap.h:827 [inline]
 #1: ffff888079163518 (&chan->lock/1){+.+.}-{4:4}, at: l2cap_sock_shutdown+0x9c9/0x10c0 net/bluetooth/l2cap_sock.c:1360

stack backtrace:
CPU: 0 UID: 0 PID: 6578 Comm: syz.0.16 Not tainted 6.14.0-rc1-next-20250207-syzkaller-02219-ged58d103e6da-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2076
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
 l2cap_sock_shutdown+0xa41/0x10c0 net/bluetooth/l2cap_sock.c:1363
 l2cap_sock_release+0x79/0x1d0 net/bluetooth/l2cap_sock.c:1419
 __sock_release net/socket.c:647 [inline]
 sock_close+0xbc/0x240 net/socket.c:1398
 __fput+0x3e9/0x9f0 fs/file_table.c:464
 task_work_run+0x24f/0x310 kernel/task_work.c:227
 get_signal+0x15f7/0x1750 kernel/signal.c:2809
 arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f32d118cda9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f32d1fa9038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 00007f32d13a5fa0 RCX: 00007f32d118cda9
RDX: 000000000000000e RSI: 0000000020000100 RDI: 0000000000000004
RBP: 00007f32d120e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f32d13a5fa0 R15: 00007ffc760ea6e8
 </TASK>


Tested on:

commit:         ed58d103 Add linux-next specific files for 20250207
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=11db0b18580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=244a34ec1429746
dashboard link: https://syzkaller.appspot.com/bug?extid=10bd8fe6741eedd2be2e
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13381df8580000