Subject: Re: [syzbot] possible deadlock in sco_conn_del

From: syzbot <[email-masked]>
Date: Mon, 11 Apr 2022 11:51:20 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    d12d7e1cfe38 Add linux-next specific files for 20220411
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=162e29a8f00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=58fcaf7d8df169a6
dashboard link: https://syzkaller.appspot.com/bug?extid=b825d87fe2d043e3e652
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16a2ff0f700000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=149fd2df700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

======================================================
WARNING: possible circular locking dependency detected
5.18.0-rc1-next-20220411-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor104/3623 is trying to acquire lock:
ffff88807bd9b130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1682 [inline]
ffff88807bd9b130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_conn_del+0x131/0x2c0 net/bluetooth/sco.c:197

but task is already holding lock:
ffffffff8d777e08 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1580 [inline]
ffffffff8d777e08 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xda/0x260 net/bluetooth/hci_conn.c:1458

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
       hci_connect_cfm include/net/bluetooth/hci_core.h:1565 [inline]
       hci_remote_features_evt+0x62b/0xa20 net/bluetooth/hci_event.c:3736
       hci_event_func net/bluetooth/hci_event.c:6890 [inline]
       hci_event_packet+0x7c1/0xf60 net/bluetooth/hci_event.c:6939
       hci_rx_work+0x522/0xd60 net/bluetooth/hci_core.c:3819
       process_one_work+0x996/0x1610 kernel/workqueue.c:2289
       worker_thread+0x665/0x1080 kernel/workqueue.c:2436
       kthread+0x2e9/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12f/0x1350 kernel/locking/mutex.c:747
       sco_sock_connect+0x1eb/0xa80 net/bluetooth/sco.c:593
       __sys_connect_file+0x14f/0x190 net/socket.c:1900
       __sys_connect+0x161/0x190 net/socket.c:1917
       __do_sys_connect net/socket.c:1927 [inline]
       __se_sys_connect net/socket.c:1924 [inline]
       __x64_sys_connect+0x6f/0xb0 net/socket.c:1924
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       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+0x2abe/0x5660 kernel/locking/lockdep.c:5053
       lock_acquire kernel/locking/lockdep.c:5665 [inline]
       lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5630
       lock_sock_nested+0x36/0xf0 net/core/sock.c:3314
       lock_sock include/net/sock.h:1682 [inline]
       sco_conn_del+0x131/0x2c0 net/bluetooth/sco.c:197
       sco_disconn_cfm+0x71/0xb0 net/bluetooth/sco.c:1379
       hci_disconn_cfm include/net/bluetooth/hci_core.h:1583 [inline]
       hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1458
       hci_dev_close_sync+0x567/0x1140 net/bluetooth/hci_sync.c:4152
       hci_dev_do_close+0x32/0x70 net/bluetooth/hci_core.c:553
       hci_rfkill_set_block+0x19c/0x1d0 net/bluetooth/hci_core.c:935
       rfkill_set_block+0x1f9/0x540 net/rfkill/core.c:345
       rfkill_fop_write+0x2c3/0x570 net/rfkill/core.c:1286
       vfs_write+0x269/0xac0 fs/read_write.c:589
       ksys_write+0x1e8/0x250 fs/read_write.c:644
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> &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(sk_lock-AF_BLUETOOTH-BTPROTO_SCO);

 *** DEADLOCK ***

4 locks held by syz-executor104/3623:
 #0: ffffffff8d9583a8 (rfkill_global_mutex){+.+.}-{3:3}, at: rfkill_fop_write+0x15c/0x570 net/rfkill/core.c:1278
 #1: ffff888022e89048 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x2a/0x70 net/bluetooth/hci_core.c:551
 #2: ffff888022e88078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x26d/0x1140 net/bluetooth/hci_sync.c:4139
 #3: ffffffff8d777e08 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:1580 [inline]
 #3: ffffffff8d777e08 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xda/0x260 net/bluetooth/hci_conn.c:1458

stack backtrace:
CPU: 0 PID: 3623 Comm: syz-executor104 Not tainted 5.18.0-rc1-next-20220411-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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+0x2abe/0x5660 kernel/locking/lockdep.c:5053
 lock_acquire kernel/locking/lockdep.c:5665 [inline]
 lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5630
 lock_sock_nested+0x36/0xf0 net/core/sock.c:3314
 lock_sock include/net/sock.h:1682 [inline]
 sco_conn_del+0x131/0x2c0 net/bluetooth/sco.c:197
 sco_disconn_cfm+0x71/0xb0 net/bluetooth/sco.c:1379
 hci_disconn_cfm include/net/bluetooth/hci_core.h:1583 [inline]
 hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1458
 hci_dev_close_sync+0x567/0x1140 net/bluetooth/hci_sync.c:4152
 hci_dev_do_close+0x32/0x70 net/bluetooth/hci_core.c:553
 hci_rfkill_set_block+0x19c/0x1d0 net/bluetooth/hci_core.c:935
 rfkill_set_block+0x1f9/0x540 net/rfkill/core.c:345
 rfkill_fop_write+0x2c3/0x570 net/rfkill/core.c:1286
 vfs_write+0x269/0xac0 fs/read_write.c:589
 ksys_write+0x1e8/0x250 fs/read_write.c:644
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f841a998629
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f841a1472f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f841aa214c0 RCX: 00007f841a998629
RDX: 0000000000000008 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff20c0bcce
R13: 00007fff20c0bccf R14: 00007f841aa214c8 R15: 0000000000022000
 </TASK>