INFO: task hung in __flush

INFO: task hung in __flush_work
Status: upstream: reported C repro on 2019/02/16 07:01
Reported-by: syzbot+aa0b64a57e300a1c6bcc@syzkaller.appspotmail.com
First crash: 1251d, last: 621d

Cause bisection: introduced by (bisect log) :
commit a42055e8d2c30d4decfc13ce943d09c7b9dad221
Author: Vakul Garg <vakul.garg@nxp.com>
Date: Fri Sep 21 04:16:13 2018 +0000

net/tls: Add support for async encryption of records for performance

Crash: INFO: task hung in tls_sw_free_resources_tx (log)
Repro: C syz .config

Fix bisection: failed (bisect log)

similar bugs (1):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.19	INFO: task hung in __flush_work	syz		done	6	563d	1012d	1/1	fixed on 2020/08/12 22:58

Sample crash report:

TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
INFO: task syz-executor925:7871 blocked for more than 140 seconds.
      Not tainted 4.20.0-rc7+ #360
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor925 D19912  7871   7870 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2831 [inline]
 __schedule+0x86c/0x1ed0 kernel/sched/core.c:3472
 schedule+0xfe/0x460 kernel/sched/core.c:3516
 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780
 do_wait_for_common kernel/sched/completion.c:83 [inline]
 __wait_for_common kernel/sched/completion.c:104 [inline]
 wait_for_common kernel/sched/completion.c:115 [inline]
 wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136
 __flush_work+0x59c/0x9b0 kernel/workqueue.c:2917
 __cancel_work_timer+0x4ba/0x820 kernel/workqueue.c:3004
 cancel_delayed_work_sync+0x1a/0x20 kernel/workqueue.c:3136
 tls_sw_free_resources_tx+0x1df/0xcf0 net/tls/tls_sw.c:1795
 tls_sk_proto_close+0x602/0x750 net/tls/tls_main.c:280
 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:428
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:458
 __sock_release+0xd7/0x250 net/socket.c:579
 sock_close+0x19/0x20 net/socket.c:1141
 __fput+0x385/0xa30 fs/file_table.c:278
 ____fput+0x15/0x20 fs/file_table.c:309
 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x401010
Code: 01 f0 ff ff 0f 83 b0 0a 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 83 3d bd 16 2d 00 00 75 14 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 84 0a 00 00 c3 48 83 ec 08 e8 3a 01 00 00
RSP: 002b:00007ffec7856f48 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000401010
RDX: 00000000e0ffffff RSI: 00000000200005c0 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f20
R13: 0000000000401fb0 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:
2 locks held by kworker/0:0/5:
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:218 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 000000006d11dec0 ((wq_completion)"events"){+.+.}, at: process_one_work+0xb43/0x1c40 kernel/workqueue.c:2124
 #1: 00000000ccfe6c9a ((work_completion)(&(&sw_ctx_tx->tx_work.work)->work)){+.+.}, at: process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128
1 lock held by khungtaskd/1014:
 #0: 00000000153ed952 (rcu_read_lock){....}, at: debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4379
1 lock held by rsyslogd/7757:
 #0: 0000000034b64696 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1bb/0x200 fs/file.c:766
2 locks held by getty/7847:
 #0: 00000000d063ffb7 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 0000000045d4d183 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7848:
 #0: 00000000dda11696 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 00000000a02eb135 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7849:
 #0: 0000000013f4e4e1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 00000000f6bb4c99 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7850:
 #0: 00000000daef1117 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 00000000229b8dfc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7851:
 #0: 000000005093d448 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 00000000bca705ed (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7852:
 #0: 000000000f124289 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 00000000a9adbb34 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by getty/7853:
 #0: 0000000027476b58 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353
 #1: 000000007cc578ce (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1e80 drivers/tty/n_tty.c:2154
2 locks held by syz-executor925/7871:
 #0: 00000000997b6df5 (&sb->s_type->i_mutex_key#11){+.+.}, at: inode_lock include/linux/fs.h:757 [inline]
 #0: 00000000997b6df5 (&sb->s_type->i_mutex_key#11){+.+.}, at: __sock_release+0x8b/0x250 net/socket.c:578
 #1: 00000000af711cb5 (sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1502 [inline]
 #1: 00000000af711cb5 (sk_lock-AF_INET6){+.+.}, at: wait_on_pending_writer+0x27c/0x5b0 net/tls/tls_main.c:89

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

NMI backtrace for cpu 1
CPU: 1 PID: 1014 Comm: khungtaskd Not tainted 4.20.0-rc7+ #360
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+0x1d3/0x2c6 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.4+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1c2/0x22c 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:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
 watchdog+0xb51/0x1060 kernel/hung_task.c:289
 kthread+0x35a/0x440 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
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

Crashes (1440):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro
ci-upstream-net-kasan-gce	2018/12/26 03:00	net-next	90cadbbf341d	8a41a0ad	.config	log	report	syz	C
ci-upstream-kasan-gce-root	2019/04/15 01:24	upstream	4443f8e6ac77	505ab413	.config	log	report	syz
ci-upstream-kasan-gce-root	2019/01/27 19:34	upstream	ba6069759381	c73f090a	.config	log	report	syz
ci-upstream-kasan-gce-root	2018/09/04 11:11	upstream	60c1f89241d4	a4718693	.config	log	report	syz
ci-upstream-linux-next-kasan-gce-root	2019/04/15 02:52	linux-next	bcb67f0fbce9	505ab413	.config	log	report	syz
ci-upstream-kasan-gce-root	2019/08/07 23:48	upstream	33920f1ec5bf	e6ebef88	.config	log	report
ci-upstream-kasan-gce	2019/08/04 02:26	upstream	dcb8cfbd8fe9	6affd8e8	.config	log	report
ci-upstream-kasan-gce	2019/07/29 13:57	upstream	609488bc979f	c85e1c5b	.config	log	report
ci-upstream-kasan-gce-selinux-root	2019/06/25 21:51	upstream	249155c20f9b	0a8d1a96	.config	log	report
ci-upstream-kasan-gce-smack-root	2019/06/10 17:57	upstream	d1fdb6d8f6a4	0159583c	.config	log	report
ci-upstream-kasan-gce-root	2018/08/26 04:54	upstream	b8dcdab36f53	76e7c3df	.config	log	report
ci-upstream-kasan-gce-386	2019/02/11 02:36	upstream	df3865f8f568	b4f792e4	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/08 22:19	net	33920f1ec5bf	e6ebef88	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/08 16:13	net	33920f1ec5bf	e6ebef88	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/07 12:17	net	33920f1ec5bf	cdde7486	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/06 21:19	net	107e47cc80ec	c6f01e54	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/05 14:19	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/05 12:09	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/05 08:14	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/05 00:02	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/04 12:47	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/03 22:27	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/03 14:19	net	107e47cc80ec	6affd8e8	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/01 06:08	net	107e47cc80ec	c692b5bd	.config	log	report
ci-upstream-net-this-kasan-gce	2019/08/01 01:22	net	107e47cc80ec	c692b5bd	.config	log	report
ci-upstream-net-this-kasan-gce	2019/07/31 22:19	net	107e47cc80ec	c692b5bd	.config	log	report
ci-upstream-net-this-kasan-gce	2019/07/29 10:37	net	107e47cc80ec	c85e1c5b	.config	log	report
ci-upstream-net-this-kasan-gce	2019/07/29 05:37	net	107e47cc80ec	c85e1c5b	.config	log	report
ci-upstream-net-this-kasan-gce	2019/07/28 23:45	net	107e47cc80ec	c85e1c5b	.config	log	report
ci-upstream-net-kasan-gce	2019/08/08 20:18	net-next	13dfb3fa4943	e6ebef88	.config	log	report
ci-upstream-net-kasan-gce	2019/08/08 18:55	net-next	13dfb3fa4943	e6ebef88	.config	log	report
ci-upstream-net-kasan-gce	2019/08/08 17:45	net-next	13dfb3fa4943	e6ebef88	.config	log	report
ci-upstream-net-kasan-gce	2019/08/08 12:44	net-next	13dfb3fa4943	e6ebef88	.config	log	report
ci-upstream-net-kasan-gce	2019/08/08 06:46	net-next	13dfb3fa4943	e6ebef88	.config	log	report
ci-upstream-net-kasan-gce	2019/08/07 13:21	net-next	13dfb3fa4943	cdde7486	.config	log	report
ci-upstream-net-kasan-gce	2019/08/07 05:19	net-next	31cc088a4f5d	c6f01e54	.config	log	report
ci-upstream-net-kasan-gce	2019/08/07 00:37	net-next	31cc088a4f5d	c6f01e54	.config	log	report
ci-upstream-net-kasan-gce	2019/08/06 12:54	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/06 02:03	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/05 22:26	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/05 17:32	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/05 06:01	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/05 02:41	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/04 07:47	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/04 06:32	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/04 01:21	net-next	31cc088a4f5d	6affd8e8	.config	log	report
ci-upstream-net-kasan-gce	2019/08/02 13:42	net-next	31cc088a4f5d	835dffe7	.config	log	report
ci-upstream-net-kasan-gce	2019/08/02 12:36	net-next	31cc088a4f5d	835dffe7	.config	log	report
ci-upstream-net-kasan-gce	2019/08/02 08:16	net-next	31cc088a4f5d	835dffe7	.config	log	report
ci-upstream-net-kasan-gce	2019/08/02 05:48	net-next	31cc088a4f5d	835dffe7	.config	log	report
ci-upstream-net-kasan-gce	2019/08/01 19:36	net-next	31cc088a4f5d	835dffe7	.config	log	report
ci-upstream-net-kasan-gce	2019/07/31 10:08	net-next	31cc088a4f5d	7c7ded69	.config	log	report
ci-upstream-net-kasan-gce	2019/07/31 01:50	net-next	31cc088a4f5d	7c7ded69	.config	log	report
ci-upstream-net-kasan-gce	2019/07/30 16:02	net-next	31cc088a4f5d	f28bf2a5	.config	log	report
ci-upstream-net-kasan-gce	2019/07/30 04:50	net-next	31cc088a4f5d	f67095ee	.config	log	report
ci-upstream-net-kasan-gce	2019/07/30 00:29	net-next	31cc088a4f5d	f67095ee	.config	log	report
ci-upstream-net-kasan-gce	2019/07/29 06:44	net-next	31cc088a4f5d	c85e1c5b	.config	log	report
ci-upstream-net-kasan-gce	2019/07/29 04:35	net-next	31cc088a4f5d	c85e1c5b	.config	log	report
ci-upstream-net-kasan-gce	2019/07/29 01:01	net-next	31cc088a4f5d	c85e1c5b	.config	log	report
ci-upstream-linux-next-kasan-gce-root	2019/07/20 21:38	linux-next	6d21a41b7b1f	1656845f	.config	log	report