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* [syzbot] INFO: task hung in rfcomm_run
@ 2021-08-17 12:03 syzbot
  0 siblings, 0 replies; only message in thread
From: syzbot @ 2021-08-17 12:03 UTC (permalink / raw)
  To: davem, desmondcheongzx, johan.hedberg, kuba, linux-bluetooth,
	linux-kernel, luiz.dentz, luiz.von.dentz, marcel, netdev,


syzbot found the following issue on:

HEAD commit:    8ca403f3e7a2 Add linux-next specific files for 20210811
git tree:       linux-next
console output:
kernel config:
dashboard link:
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:
C reproducer:

The issue was bisected to:

commit b7ce436a5d798bc59e71797952566608a4b4626b
Author: Desmond Cheong Zhi Xi <>
Date:   Tue Aug 10 04:14:09 2021 +0000

    Bluetooth: switch to lock_sock in RFCOMM

bisection log:
final oops:
console output:

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Fixes: b7ce436a5d79 ("Bluetooth: switch to lock_sock in RFCOMM")

INFO: task krfcommd:2895 blocked for more than 143 seconds.
      Not tainted 5.14.0-rc5-next-20210811-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:krfcommd        state:D stack:29640 pid: 2895 ppid:     2 flags:0x00004000
Call Trace:
 context_switch kernel/sched/core.c:4698 [inline]
 __schedule+0x93a/0x26f0 kernel/sched/core.c:5955
 schedule+0xd3/0x270 kernel/sched/core.c:6034
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6093
 __mutex_lock_common kernel/locking/mutex.c:1036 [inline]
 __mutex_lock+0xa46/0x1300 kernel/locking/mutex.c:1096
 rfcomm_process_sessions net/bluetooth/rfcomm/core.c:1979 [inline]
 rfcomm_run+0x2ed/0x4a20 net/bluetooth/rfcomm/core.c:2086
 kthread+0x3e5/0x4d0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
INFO: task syz-executor247:6597 blocked for more than 143 seconds.
      Not tainted 5.14.0-rc5-next-20210811-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor247 state:D stack:27600 pid: 6597 ppid:  6565 flags:0x00004006
Call Trace:
 context_switch kernel/sched/core.c:4698 [inline]
 __schedule+0x93a/0x26f0 kernel/sched/core.c:5955
 schedule+0xd3/0x270 kernel/sched/core.c:6034
 __lock_sock+0x13d/0x260 net/core/sock.c:2645
 lock_sock_nested+0xf6/0x120 net/core/sock.c:3178
 lock_sock include/net/sock.h:1612 [inline]
 rfcomm_sk_state_change+0xb4/0x390 net/bluetooth/rfcomm/sock.c:73
 __rfcomm_dlc_close+0x1b6/0x8a0 net/bluetooth/rfcomm/core.c:489
 rfcomm_dlc_close+0x1ea/0x240 net/bluetooth/rfcomm/core.c:520
 __rfcomm_sock_close+0xac/0x260 net/bluetooth/rfcomm/sock.c:220
 rfcomm_sock_shutdown+0xe9/0x210 net/bluetooth/rfcomm/sock.c:931
 rfcomm_sock_release+0x5f/0x140 net/bluetooth/rfcomm/sock.c:951
 __sock_release+0xcd/0x280 net/socket.c:649
 sock_close+0x18/0x20 net/socket.c:1311
 __fput+0x288/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 exit_task_work include/linux/task_work.h:32 [inline]
 do_exit+0xbd4/0x2a60 kernel/exit.c:825
 do_group_exit+0x125/0x310 kernel/exit.c:922
 get_signal+0x47f/0x2160 kernel/signal.c:2831
 arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:865
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
RIP: 0033:0x446009
RSP: 002b:00007ffda734ed78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 0000000000000003 RCX: 0000000000446009
RDX: 0000000000000080 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 0000000000000003 R08: 000000ff00000001 R09: 000000ff00000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001dee2b8
R13: 0000000000000072 R14: 00007ffda734edd0 R15: 0000000000000003
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.14.0-rc5-next-20210811-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1ae/0x220 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:254 [inline]
 watchdog+0xcb7/0xed0 kernel/hung_task.c:339
 kthread+0x3e5/0x4d0 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x1c6/0x250 drivers/acpi/processor_idle.c:553

This report is generated by a bot. It may contain errors.
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For information about bisection process see:
syzbot can test patches for this issue, for details see:

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2021-08-17 12:03 [syzbot] INFO: task hung in rfcomm_run syzbot

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