Re: [syzbot] [bluetooth?] INFO: task hung in hci_conn_failed

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in hci_conn_failed

INFO: task kworker/u5:4:5429 blocked for more than 143 seconds.
      Not tainted 6.8.0-rc2-syzkaller-g861c0981648f-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u5:4    state:D stack:27616 pid:5429  tgid:5429  ppid:2      flags:0x00004000
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5400 [inline]
 __schedule+0xf12/0x5c00 kernel/sched/core.c:6727
 __schedule_loop kernel/sched/core.c:6802 [inline]
 schedule+0xe9/0x270 kernel/sched/core.c:6817
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6874
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x5b9/0x9d0 kernel/locking/mutex.c:752
 hci_connect_cfm include/net/bluetooth/hci_core.h:1983 [inline]
 hci_conn_failed+0x158/0x370 net/bluetooth/hci_conn.c:1289
 hci_abort_conn_sync+0x758/0xb50 net/bluetooth/hci_sync.c:5356
 abort_conn_sync+0x187/0x390 net/bluetooth/hci_conn.c:2988
 hci_cmd_sync_work+0x1a4/0x410 net/bluetooth/hci_sync.c:306
 process_one_work+0x886/0x15d0 kernel/workqueue.c:2633
 process_scheduled_works kernel/workqueue.c:2706 [inline]
 worker_thread+0x8b9/0x1290 kernel/workqueue.c:2787
 kthread+0x2c6/0x3a0 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/8:
3 locks held by kworker/0:1/9:
2 locks held by kworker/u4:0/11:
 #0: ffff888013089938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x789/0x15d0 kernel/workqueue.c:2608
 #1: ffffc90000107d80 (connector_reaper_work){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2609
2 locks held by kworker/u4:2/42:
 #0: ffff888013089938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x789/0x15d0 kernel/workqueue.c:2608
 #1: ffffc90000b2fd80 ((reaper_work).work){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2609
1 lock held by udevd/4510:
2 locks held by getty/4809:
 #0: ffff8880298450a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xfc6/0x1490 drivers/tty/n_tty.c:2201
1 lock held by syz-executor.3/5419:
5 locks held by kworker/u5:4/5429:
 #0: ffff88802d96d538 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x789/0x15d0 kernel/workqueue.c:2608
 #1: ffffc90009befd80 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2609
 #2: ffff888075635060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x170/0x410 net/bluetooth/hci_sync.c:305
 #3: ffff888075634078 (&hdev->lock){+.+.}-{3:3}, at: hci_abort_conn_sync+0x150/0xb50 net/bluetooth/hci_sync.c:5337
 #4: ffffffff8ef238c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:1983 [inline]
 #4: ffffffff8ef238c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_failed+0x158/0x370 net/bluetooth/hci_conn.c:1289
6 locks held by kworker/u5:5/5431:
 #0: ffff888027f29538 ((wq_completion)hci5){+.+.}-{0:0}, at: process_one_work+0x789/0x15d0 kernel/workqueue.c:2608
 #1: ffffc90009bffd80 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work+0x7eb/0x15d0 kernel/workqueue.c:2609
 #2: ffff888079359060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x170/0x410 net/bluetooth/hci_sync.c:305
 #3: ffff888079358078 (&hdev->lock){+.+.}-{3:3}, at: hci_abort_conn_sync+0x150/0xb50 net/bluetooth/hci_sync.c:5337
 #4: ffffffff8ef238c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_connect_cfm include/net/bluetooth/hci_core.h:1983 [inline]
 #4: ffffffff8ef238c8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_failed+0x158/0x370 net/bluetooth/hci_conn.c:1289
 #5: ffffffff8d1b8438 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #5: ffffffff8d1b8438 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3ff/0x800 kernel/rcu/tree_exp.h:995
3 locks held by kworker/1:5/5500:
3 locks held by kworker/0:8/5556:
3 locks held by kworker/1:6/5586:
3 locks held by kworker/1:7/5659:
2 locks held by dhcpcd/20271:
 #0: ffff88808e304130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff88808e304130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3202
 #1: ffffffff8d1b8438 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
 #1: ffffffff8d1b8438 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3ff/0x800 kernel/rcu/tree_exp.h:995
1 lock held by dhcpcd/20354:
 #0: ffff88803a7ba130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff88803a7ba130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3202
1 lock held by dhcpcd/20466:
 #0: ffff88801db68130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff88801db68130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3202
1 lock held by dhcpcd/20585:
 #0: ffff888094ba4130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff888094ba4130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3202
1 lock held by dhcpcd/20736:
 #0: ffff88809175e130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1691 [inline]
 #0: ffff88809175e130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x2c/0xf50 net/packet/af_packet.c:3202
1 lock held by syz-executor.1/21229:
3 locks held by syz-executor.4/21232:
1 lock held by syz-executor.5/21233:

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted 6.8.0-rc2-syzkaller-g861c0981648f-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x277/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x299/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf87/0x1210 kernel/hung_task.c:379
 kthread+0x2c6/0x3a0 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 21255 Comm: syz-executor.0 Not tainted 6.8.0-rc2-syzkaller-g861c0981648f-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:__debug_check_no_obj_freed lib/debugobjects.c:981 [inline]
RIP: 0010:debug_check_no_obj_freed+0x21d/0x600 lib/debugobjects.c:1019
Code: 89 64 24 38 49 bd 22 01 00 00 00 00 ad de 48 c1 ea 03 4d 89 fc 80 3c 1a 00 0f 85 dc 00 00 00 48 8d 78 18 41 83 c6 01 4c 8b 38 <48> 89 fa 48 c1 ea 03 80 3c 1a 00 0f 85 f7 02 00 00 48 8b 50 18 4c
RSP: 0018:ffffc9007e76fc80 EFLAGS: 00000006
RAX: ffff88809414c528 RBX: dffffc0000000000 RCX: ffffffff8168ea5e
RDX: 1ffff110128298a5 RSI: ffff888066342100 RDI: ffff88809414c540
RBP: ffffc9007e76fdc0 R08: 0000000000000001 R09: fffff5200fcedf7e
R10: 0000000000000003 R11: 0000000000000000 R12: ffff888066341100
R13: dead000000000122 R14: 0000000000000005 R15: ffff88805dc630f0
FS:  0000555555f24480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007faacb501400 CR3: 0000000048e71000 CR4: 0000000000350ef0
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 slab_free_hook mm/slub.c:2093 [inline]
 slab_free mm/slub.c:4299 [inline]
 kmem_cache_free+0x255/0x350 mm/slub.c:4363
 putname+0x12e/0x170 fs/namei.c:274
 do_symlinkat+0x1ac/0x310 fs/namei.c:4515
 __do_sys_symlinkat fs/namei.c:4522 [inline]
 __se_sys_symlinkat fs/namei.c:4519 [inline]
 __x64_sys_symlinkat+0x97/0xc0 fs/namei.c:4519
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xd3/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7faacb47c527
Code: 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0a 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd9c121f28 EFLAGS: 00000206 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007ffd9c121ff0 RCX: 00007faacb47c527
RDX: 00007faacb4c9526 RSI: 00000000ffffff9c RDI: 00007ffd9c121ff0
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffd9c121c77
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
 </TASK>


Tested on:

commit:         861c0981 Merge tag 'jfs-6.8-rc3' of github.com:kleikam..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1207db37e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b168fa511db3ca08
dashboard link: https://syzkaller.appspot.com/bug?extid=a984066a63e9c1e62662
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14a550d3e80000