INFO: task hung in ip6gre_exit_batch_net

From: syzbot
Date: Mon Jun 04 2018 - 11:03:35 EST

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Hello,

syzbot found the following crash on:

HEAD commit: bc2dbc5420e8 Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164e42b7800000
kernel config: https://syzkaller.appspot.com/x/.config?x=982e2df1b9e60b02
dashboard link: https://syzkaller.appspot.com/bug?extid=bf78a74f82c1cf19069e
compiler: gcc (GCC) 8.0.1 20180413 (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+bf78a74f82c1cf19069e@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task kworker/u4:1:22 blocked for more than 120 seconds.
Not tainted 4.17.0-rc6+ #68
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1 D13944 22 2 0x80000000
Workqueue: netns cleanup_net
Call Trace:
context_switch kernel/sched/core.c:2859 [inline]
__schedule+0x801/0x1e30 kernel/sched/core.c:3501
schedule+0xef/0x430 kernel/sched/core.c:3545
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3603
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0xe38/0x17f0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
ip6gre_exit_batch_net+0xd5/0x7d0 net/ipv6/ip6_gre.c:1585
ops_exit_list.isra.7+0x105/0x160 net/core/net_namespace.c:155
cleanup_net+0x51d/0xb20 net/core/net_namespace.c:523
process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Showing all locks held in the system:
4 locks held by kworker/u4:1/22:
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 0000000049a7b590 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
#1: 0000000030a00b6b (net_cleanup_work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
#2: 000000007eb35e65 (pernet_ops_rwsem){++++}, at: cleanup_net+0x11a/0xb20 net/core/net_namespace.c:490
#3: 000000007eb32c75 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
3 locks held by kworker/1:1/24:
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 000000001c9e6580 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
#1: 000000009edcfbe7 ((addr_chk_work).work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
#2: 000000007eb32c75 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
2 locks held by khungtaskd/893:
#0: 000000007eeb621a (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: 000000007eeb621a (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249
#1: 00000000239f1b5e (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
2 locks held by getty/4481:
#0: 00000000cc114025 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000006ad1f3fc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4482:
#0: 00000000226a16cc (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000008cee8cdc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4483:
#0: 0000000067bd3c39 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000005d8bc81d (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4484:
#0: 00000000f0f8d839 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000a9d5f091 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4485:
#0: 000000002c96ee9a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000033338ac7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4486:
#0: 00000000f6db39b5 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000bb7c6099 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4487:
#0: 000000006be9659d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000e2edd3d0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
3 locks held by kworker/1:3/27147:
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 00000000c208aa7f ((wq_completion)"events"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
#1: 00000000fa87e61f (deferred_process_work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
#2: 000000007eb32c75 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
1 lock held by syz-executor7/29665:
#0: 000000006e20d618 (sk_lock-AF_INET6){+.+.}, at: lock_sock include/net/sock.h:1469 [inline]
#0: 000000006e20d618 (sk_lock-AF_INET6){+.+.}, at: tls_sw_sendmsg+0x1b9/0x12e0 net/tls/tls_sw.c:384
1 lock held by syz-executor7/29689:
#0: 000000007eb32c75 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74

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

NMI backtrace for cpu 0
CPU: 0 PID: 893 Comm: khungtaskd Not tainted 4.17.0-rc6+ #68
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+0x1b9/0x294 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x151/0x192 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:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0xc10/0xf60 kernel/hung_task.c:249
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54

---
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Next message: Bjorn Andersson: "Re: [PATCH 2/2] tsens: Get rid of unused fields in structure"
Previous message: David Howells: "Re: [PATCH 32/32] [RFC] fsinfo: Add a system call to allow querying of filesystem information [ver #8]"
Next in thread: Dmitry Vyukov: "Re: INFO: task hung in ip6gre_exit_batch_net"
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