INFO: task hung in mkiss_close

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 106fa147 Linux 4.19.127
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=114eb432100000
kernel config: https://syzkaller.appspot.com/x/.config?x=b4a714eef836e3f3
dashboard link: https://syzkaller.appspot.com/bug?extid=3408ec7ca303a2e6c0b0
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3408ec...@syzkaller.appspotmail.com

INFO: task syz-executor.2:16847 blocked for more than 140 seconds.
Not tainted 4.19.127-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D27704 16847 6611 0x00000006
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x8a2/0x1fc0 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_timeout+0x8f3/0xed0 kernel/time/timer.c:1782
do_wait_for_common kernel/sched/completion.c:83 [inline]
__wait_for_common kernel/sched/completion.c:104 [inline]
wait_for_common+0x29c/0x470 kernel/sched/completion.c:115
__flush_work+0x48b/0x870 kernel/workqueue.c:2928
flush_all_backlogs net/core/dev.c:5289 [inline]
rollback_registered_many+0x493/0xc40 net/core/dev.c:8178
rollback_registered+0xf2/0x1c0 net/core/dev.c:8235
unregister_netdevice_queue+0x1d7/0x2b0 net/core/dev.c:9290
unregister_netdevice include/linux/netdevice.h:2614 [inline]
unregister_netdev+0x18/0x20 net/core/dev.c:9331
mkiss_close+0x17d/0x1f0 drivers/net/hamradio/mkiss.c:812
tty_ldisc_close.isra.0+0xa2/0xd0 drivers/tty/tty_ldisc.c:493
tty_ldisc_kill+0x46/0xc0 drivers/tty/tty_ldisc.c:639
tty_ldisc_release+0xbe/0x270 drivers/tty/tty_ldisc.c:806
tty_release_struct+0x16/0x50 drivers/tty/tty_io.c:1611
tty_release+0xbc9/0xe90 drivers/tty/tty_io.c:1784
__fput+0x2cd/0x890 fs/file_table.c:278
task_work_run+0x13f/0x1b0 kernel/task_work.c:113
get_signal+0x1b2e/0x1f30 kernel/signal.c:2399
do_signal+0x8f/0x1620 arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45ca69
Code: Bad RIP value.
RSP: 002b:00007fa08bc60c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00000000004ef500 RCX: 000000000045ca69
RDX: 0000000020000000 RSI: 0000000000005423 RDI: 0000000000000004
RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000591 R14: 00000000004c84da R15: 00007fa08bc616d4

Showing all locks held in the system:
1 lock held by khungtaskd/1077:
#0: 00000000e05e7060 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
1 lock held by systemd-journal/3684:
1 lock held by in:imklog/6196:
1 lock held by syz-executor.3/15008:
4 locks held by syz-executor.2/16847:
#0: 00000000829803a9 (&tty->ldisc_sem){++++}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:320 [inline]
#0: 00000000829803a9 (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:376 [inline]
#0: 00000000829803a9 (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:397 [inline]
#0: 00000000829803a9 (&tty->ldisc_sem){++++}, at: tty_ldisc_release+0x104/0x270 drivers/tty/tty_ldisc.c:805
#1: 000000002fa7584f (&tty->ldisc_sem/1){+.+.}, at: __tty_ldisc_lock_nested drivers/tty/tty_ldisc.c:326 [inline]
#1: 000000002fa7584f (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:378 [inline]
#1: 000000002fa7584f (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:397 [inline]
#1: 000000002fa7584f (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_release+0x19a/0x270 drivers/tty/tty_ldisc.c:805
#2: 000000007d33f6cc (rtnl_mutex){+.+.}, at: unregister_netdev+0xe/0x20 net/core/dev.c:9330
#3: 000000006ee47484 (cpu_hotplug_lock.rw_sem){++++}, at: get_online_cpus include/linux/cpu.h:137 [inline]
#3: 000000006ee47484 (cpu_hotplug_lock.rw_sem){++++}, at: flush_all_backlogs net/core/dev.c:5282 [inline]
#3: 000000006ee47484 (cpu_hotplug_lock.rw_sem){++++}, at: rollback_registered_many+0x387/0xc40 net/core/dev.c:8178
1 lock held by systemd-udevd/16903:
#0: 000000007d33f6cc (rtnl_mutex){+.+.}, at: dev_ioctl+0x4b8/0xc58 net/core/dev_ioctl.c:422

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

NMI backtrace for cpu 1
CPU: 1 PID: 1077 Comm: khungtaskd Not tainted 4.19.127-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x962/0xe40 kernel/hung_task.c:287
kthread+0x30b/0x410 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 15008 Comm: syz-executor.3 Not tainted 4.19.127-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:unwind_next_frame+0xecf/0x1b10 arch/x86/kernel/unwind_orc.c:513
Code: 48 8b 4c 24 20 80 3c 02 00 4c 8b 44 24 28 0f 85 80 08 00 00 48 8b 14 24 4d 89 67 38 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 3e 08 00 00 49 8d 7f 58 49 c7 47 50 00 00 00 00
RSP: 0000:ffff888054537888 EFLAGS: 00000806
RAX: dffffc0000000000 RBX: 1ffff1100a8a6f19 RCX: ffffffff89eb5748
RDX: 1ffff1100a8a6f36 RSI: ffff888054537820 RDI: ffff888054537ef0
RBP: 0000000000000001 R08: ffffffff89eb574c R09: 0000000000000001
R10: 000000000000815f R11: 0000000000064061 R12: ffff888054537ef8
R13: ffff888054537995 R14: ffff888054537998 R15: ffff888054537960
FS: 00007f0bbdb9f700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000488a8ef8 CR3: 00000000a065c000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__save_stack_trace+0x83/0x100 arch/x86/kernel/stacktrace.c:44
save_stack mm/kasan/kasan.c:448 [inline]
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x128/0x1f0 mm/kasan/kasan.c:521
__cache_free mm/slab.c:3503 [inline]
kmem_cache_free+0x7f/0x260 mm/slab.c:3765
__sigqueue_free kernel/signal.c:447 [inline]
dequeue_synchronous_signal kernel/signal.c:736 [inline]
get_signal+0xd7c/0x1f30 kernel/signal.c:2478
do_signal+0x8f/0x1620 arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163
prepare_exit_to_usermode+0x27b/0x2e0 arch/x86/entry/common.c:198
retint_user+0x8/0x18
RIP: 0033:0x405dd9
Code: d0 ff ff ff 01 48 8b 7c 24 28 c7 44 24 34 00 00 00 00 e8 0a ef 01 00 85 c0 75 23 48 6b 44 24 20 18 8b 7c 24 1c 48 03 44 24 38 <48> 8b 48 10 48 8b 50 08 48 8b 30 e8 a7 0a 01 00 89 44 24 34 64 f0
RSP: 002b:00007f0bbdb9ea70 EFLAGS: 00010206
RAX: 00000000488a8ee8 RBX: 0000000000509440 RCX: 00000000004168c7
RDX: 2a670cae5c3e4a1d RSI: 0000000000000000 RDI: 0000000000000007
RBP: 000000000078c0e0 R08: 00007f0bbdb9ea70 R09: 000000000078c0e0
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
R13: 0000000000000c0e R14: 00000000004ce5f6 R15: 00007f0bbdb9f6d4


---
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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.