INFO: task hung in tipc_nametbl_stop

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 30bfd9306281 net/ipv6: do not copy dst flags on rt init
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=130f76fa400000
kernel config: https://syzkaller.appspot.com/x/.config?x=b8f349d23d3c4835
dashboard link: https://syzkaller.appspot.com/bug?extid=33479e56802ca6725b12
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [da...@davemloft.net jon....@ericsson.com
linux-...@vger.kernel.org net...@vger.kernel.org
tipc-di...@lists.sourceforge.net ying...@windriver.com]

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+33479e...@syzkaller.appspotmail.com

ip6_tunnel: M ,�Œ z xmit: Local address not yet configured!
ip6_tunnel: M ,�Œ z xmit: Local address not yet configured!
ip6_tunnel: M ,�Œ z xmit: Local address not yet configured!
ip6_tunnel: M ,�Œ z xmit: Local address not yet configured!
ip6_tunnel: M ,�Œ z xmit: Local address not yet configured!
INFO: task syz-executor1:6191 blocked for more than 140 seconds.
Not tainted 4.19.0-rc3+ #103
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1 D22952 6191 5429 0x80000004
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
schedule+0xfe/0x460 kernel/sched/core.c:3517
exp_funnel_lock kernel/rcu/tree_exp.h:320 [inline]
_synchronize_rcu_expedited+0xc68/0xfd0 kernel/rcu/tree_exp.h:667
synchronize_rcu_expedited+0x35/0xb0 kernel/rcu/tree_exp.h:795
synchronize_net+0x3b/0x60 net/core/dev.c:9012
tipc_nametbl_stop+0x968/0xca0 net/tipc/name_table.c:796
tipc_exit_net+0x2d/0x40 net/tipc/core.c:103
ops_exit_list.isra.7+0xb0/0x160 net/core/net_namespace.c:153
setup_net+0x56e/0x950 net/core/net_namespace.c:331
copy_net_ns+0x2b1/0x4a0 net/core/net_namespace.c:437
create_new_namespaces+0x6ad/0x900 kernel/nsproxy.c:107
unshare_nsproxy_namespaces+0xc3/0x1f0 kernel/nsproxy.c:206
ksys_unshare+0x79c/0x10b0 kernel/fork.c:2489
__do_sys_unshare kernel/fork.c:2557 [inline]
__se_sys_unshare kernel/fork.c:2555 [inline]
__x64_sys_unshare+0x31/0x40 kernel/fork.c:2555
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4572d9
Code: 42 08 48 8b 40 08 48 89 04 24 e8 02 d3 fc ff 48 8b 6c 24 08 48 83 c4
10 c3 e8 e3 2b 00 00 eb c1 cc 64 48 8b 0c 25 f8 ff ff ff <48> 3b 61 10 76
75 48 83 ec 38 48 89 6c 24 30 48 8d 6c 24 30 48 8b
RSP: 002b:00007fc821fa2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007fc821fa36d4 RCX: 00000000004572d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00000000009301e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d7c08 R14: 00000000004caa6a R15: 0000000000000002

Showing all locks held in the system:
1 lock held by khungtaskd/984:
#0: 00000000517afdd6 (rcu_read_lock){....}, at:
debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4436
1 lock held by rsyslogd/5210:
#0: 00000000c4c711bd (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1bb/0x200
fs/file.c:766
2 locks held by getty/5300:
#0: 00000000edff22db (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000005897cae6 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5301:
#0: 000000007a6554d2 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 00000000526ff99e (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5302:
#0: 000000005aa0e8ac (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000003e58b23f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5303:
#0: 00000000797ef51c (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000007c84f985 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5304:
#0: 00000000b14ec18a (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 00000000e1af9d1a (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5305:
#0: 00000000fccc08ad (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000004c51c19a (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/5306:
#0: 00000000021facd4 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
#1: 00000000bbe803cb (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
1 lock held by syz-executor1/6191:
#0: 000000000b25131c (pernet_ops_rwsem){++++}, at: copy_net_ns+0x28c/0x4a0
net/core/net_namespace.c:433

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

NMI backtrace for cpu 1
CPU: 1 PID: 984 Comm: khungtaskd Not tainted 4.19.0-rc3+ #103
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+0x1c4/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b3/0x1ed lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:144 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
watchdog+0xb3e/0x1050 kernel/hung_task.c:265
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:57


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[syzbot]

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