INFO: task hung in tipc_exit_net (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 66722c42ec91 Linux 4.14.256
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13e898c5b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=b8004ce84f364d9
dashboard link: https://syzkaller.appspot.com/bug?extid=3cd928f51d515eb511fe
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3cd928...@syzkaller.appspotmail.com

netlink: 28 bytes leftover after parsing attributes in process `syz-executor.1'.
INFO: task kworker/u4:0:5 blocked for more than 140 seconds.
Not tainted 4.14.256-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:0 D26248 5 2 0x80000000
Workqueue: netns cleanup_net
Call Trace:
context_switch kernel/sched/core.c:2811 [inline]
__schedule+0x88b/0x1de0 kernel/sched/core.c:3387
schedule+0x8d/0x1b0 kernel/sched/core.c:3431
schedule_timeout+0x80a/0xe90 kernel/time/timer.c:1724
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common+0x272/0x430 kernel/sched/completion.c:123
flush_workqueue+0x3ce/0x1310 kernel/workqueue.c:2677
flush_scheduled_work include/linux/workqueue.h:578 [inline]
tipc_exit_net+0x38/0x60 net/tipc/core.c:96
ops_exit_list+0xa5/0x150 net/core/net_namespace.c:142
cleanup_net+0x3b3/0x840 net/core/net_namespace.c:485
process_one_work+0x793/0x14a0 kernel/workqueue.c:2117
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2251
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Showing all locks held in the system:
3 locks held by kworker/u4:0/5:
#0: ("%s""netns"){+.+.}, at: [<ffffffff81364b80>] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2088
#1: (net_cleanup_work){+.+.}, at: [<ffffffff81364bb6>] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2092
#2: (net_mutex){+.+.}, at: [<ffffffff85c1ad70>] cleanup_net+0x110/0x840 net/core/net_namespace.c:451
1 lock held by khungtaskd/1532:
#0: (tasklist_lock){.+.+}, at: [<ffffffff8701c7c7>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
3 locks held by kworker/1:3/4645:
#0: ("events"){+.+.}, at: [<ffffffff81364b80>] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2088
#1: ((&smc->tcp_listen_work)){+.+.}, at: [<ffffffff81364bb6>] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2092
#2: (&smc->clcsock_release_lock){+.+.}, at: [<ffffffff86d3f39c>] smc_clcsock_accept net/smc/af_smc.c:600 [inline]
#2: (&smc->clcsock_release_lock){+.+.}, at: [<ffffffff86d3f39c>] smc_tcp_listen_work+0x6ac/0xb80 net/smc/af_smc.c:935
2 locks held by login/7700:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8354e1c2>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83543543>] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156
2 locks held by login/7926:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8354e1c2>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83543543>] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156
2 locks held by login/7927:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8354e1c2>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff83543543>] n_tty_read+0x1e3/0x1680 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.4/12133:
#0: (net_mutex){+.+.}, at: [<ffffffff85c1b5f6>] copy_net_ns+0x156/0x440 net/core/net_namespace.c:411

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

NMI backtrace for cpu 1
CPU: 1 PID: 1532 Comm: khungtaskd Not tainted 4.14.256-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x13a/0x180 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x5b9/0xb40 kernel/hung_task.c:274
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7969 Comm: syz-fuzzer Not tainted 4.14.256-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88809c230500 task.stack: ffff8880a8e60000
RIP: 0033:0x4214b0
RSP: 002b:000000c00003fe78 EFLAGS: 00000246
RAX: 0000000000000003 RBX: 00007fa856134840 RCX: 0000000000000002
RDX: 000000c005457a00 RSI: 0000000000000060 RDI: 00007fa855aa3953
RBP: 000000c00003fe98 R08: 000000000000001a R09: 0000000000000004
R10: 000000c00001d698 R11: 0000000000000008 R12: 000000c005457a00
R13: 000000000000009e R14: 000000000000009d R15: 0000000000000200
FS: 000000c00002e490(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbb6ee65000 CR3: 00000000af01d000 CR4: 00000000003406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

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