INFO: task hung in __tun_chr_ioctl

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
8f5fd927c3a7576d57248a2d7a0861c3f2795973 (Fri Mar 16 20:37:42 2018 +0000)
Merge tag 'for-4.16-rc5-tag' of
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a13db9...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

INFO: task syz-executor1:22250 blocked for more than 120 seconds.
Not tainted 4.16.0-rc5+ #357
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1 D25184 22250 4289 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2862 [inline]
__schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440
schedule+0xf5/0x430 kernel/sched/core.c:3499
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3557
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
__tun_chr_ioctl+0x1b1/0x40d0 drivers/net/tun.c:2810
tun_chr_ioctl+0x2a/0x40 drivers/net/tun.c:3077
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007fa8a093bc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa8a093c6d4 RCX: 0000000000453e69
RDX: 0000000020000080 RSI: 00000000400454ca RDI: 0000000000000013
RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000323 R14: 00000000006f4be8 R15: 0000000000000001

Showing all locks held in the system:
2 locks held by kworker/1:0/17:
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>] work_static
include/linux/workqueue.h:198 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
set_work_data kernel/workqueue.c:619 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084
#1: ((work_completion)(&rew.rew_work)){+.+.}, at: [<000000006415d644>]
process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088
2 locks held by khungtaskd/800:
#0: (rcu_read_lock){....}, at: [<00000000d3e58282>]
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: (rcu_read_lock){....}, at: [<00000000d3e58282>] watchdog+0x1c5/0xd60
kernel/hung_task.c:249
#1: (tasklist_lock){.+.+}, at: [<00000000590b6074>]
debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470
3 locks held by kworker/1:2/1784:
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>] work_static
include/linux/workqueue.h:198 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
set_work_data kernel/workqueue.c:619 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: ((wq_completion)"events"){+.+.}, at: [<00000000c9e8457d>]
process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084
#1: ((linkwatch_work).work){+.+.}, at: [<000000006415d644>]
process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088
#2: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
2 locks held by getty/4207:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4208:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4209:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4210:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4211:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4212:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
2 locks held by getty/4213:
#0: (&tty->ldisc_sem){++++}, at: [<000000002246b2d4>]
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000025b60669>]
n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131
3 locks held by kworker/1:3/8166:
#0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
[<00000000c9e8457d>] work_static include/linux/workqueue.h:198 [inline]
#0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
[<00000000c9e8457d>] set_work_data kernel/workqueue.c:619 [inline]
#0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
[<00000000c9e8457d>] set_work_pool_and_clear_pending kernel/workqueue.c:646
[inline]
#0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
[<00000000c9e8457d>] process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084
#1: ((addr_chk_work).work){+.+.}, at: [<000000006415d644>]
process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088
#2: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
2 locks held by syz-executor1/22242:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
#1: (rcu_sched_state.exp_mutex){+.+.}, at: [<00000000675a5f13>]
exp_funnel_lock kernel/rcu/tree_exp.h:272 [inline]
#1: (rcu_sched_state.exp_mutex){+.+.}, at: [<00000000675a5f13>]
_synchronize_rcu_expedited.constprop.72+0x9fa/0xac0
kernel/rcu/tree_exp.h:596
1 lock held by syz-executor1/22250:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor1/22253:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor0/22256:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor0/22261:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor0/22264:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor0/22265:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
2 locks held by syz-executor2/22243:
#0: (&sig->cred_guard_mutex){+.+.}, at: [<00000000096b46ba>]
SYSC_perf_event_open+0x12ca/0x2e00 kernel/events/core.c:9979
#1: (perf_sched_mutex){+.+.}, at: [<000000007096a60e>] account_event
kernel/events/core.c:9385 [inline]
#1: (perf_sched_mutex){+.+.}, at: [<000000007096a60e>]
perf_event_alloc+0x2326/0x2b00 kernel/events/core.c:9576
1 lock held by syz-executor2/22245:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor2/22259:
#0: (rtnl_mutex){+.+.}, at: [<00000000e275d2e6>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
2 locks held by syz-executor6/22247:
#0: (&sig->cred_guard_mutex){+.+.}, at: [<00000000096b46ba>]
SYSC_perf_event_open+0x12ca/0x2e00 kernel/events/core.c:9979
#1: (perf_sched_mutex){+.+.}, at: [<000000007096a60e>] account_event
kernel/events/core.c:9385 [inline]
#1: (perf_sched_mutex){+.+.}, at: [<000000007096a60e>]
perf_event_alloc+0x2326/0x2b00 kernel/events/core.c:9576
3 locks held by blkid/22275:
#0: (&bdev->bd_mutex){+.+.}, at: [<0000000012e91cb0>]
__blkdev_put+0xbc/0x760 fs/block_dev.c:1775
#1: (loop_index_mutex){+.+.}, at: [<00000000f6fa39f1>]
lo_release+0x1f/0x190 drivers/block/loop.c:1614
#2: (&lo->lo_ctl_mutex#2){+.+.}, at: [<00000000d468c386>] __lo_release
drivers/block/loop.c:1591 [inline]
#2: (&lo->lo_ctl_mutex#2){+.+.}, at: [<00000000d468c386>]
lo_release+0x85/0x190 drivers/block/loop.c:1615

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

NMI backtrace for cpu 1
CPU: 1 PID: 800 Comm: khungtaskd Not tainted 4.16.0-rc5+ #357
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+0x194/0x24d lib/dump_stack.c:53
nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x123/0x180 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+0x90c/0xd60 kernel/hung_task.c:249
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7 Comm: ksoftirqd/0 Not tainted 4.16.0-rc5+ #357
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:jhash2 include/linux/jhash.h:128 [inline]
RIP: 0010:hash_stack lib/stackdepot.c:161 [inline]
RIP: 0010:depot_save_stack+0x91/0x460 lib/stackdepot.c:230
RSP: 0000:ffff8801d9ae6cb0 EFLAGS: 00000206
RAX: 000000009be52447 RBX: 00000000c56934f1 RCX: 0000000000000006
RDX: ffff8801d9ae6d80 RSI: 0000000001090220 RDI: ffff8801d9ae6cf0
RBP: ffff8801d9ae6ce0 R08: 0000000000000012 R09: ffff8801d9ae6d08
R10: 0000000026be1269 R11: 00000000c56934f1 R12: ffff880149a6a240
R13: 0000000001090220 R14: ffff880149a6a240 R15: ffff8801dac00940
FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f382a0f3db8 CR3: 0000000006e22002 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
save_stack+0xa3/0xd0 mm/kasan/kasan.c:453
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
slab_post_alloc_hook mm/slab.h:443 [inline]
slab_alloc_node mm/slab.c:3322 [inline]
kmem_cache_alloc_node_trace+0x139/0x760 mm/slab.c:3648
__do_kmalloc_node mm/slab.c:3668 [inline]
__kmalloc_node_track_caller+0x33/0x70 mm/slab.c:3683
__kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
__alloc_skb+0x13b/0x780 net/core/skbuff.c:205
alloc_skb include/linux/skbuff.h:983 [inline]
_sctp_make_chunk+0x51/0x270 net/sctp/sm_make_chunk.c:1390
sctp_make_control+0x39/0x150 net/sctp/sm_make_chunk.c:1437
sctp_make_heartbeat+0x90/0x420 net/sctp/sm_make_chunk.c:1151
sctp_sf_heartbeat.isra.24+0x26/0x180 net/sctp/sm_statefuns.c:973
sctp_sf_sendbeat_8_3+0x36b/0x520 net/sctp/sm_statefuns.c:1017
sctp_do_sm+0x192/0x6ed0 net/sctp/sm_sideeffect.c:1178
sctp_generate_heartbeat_event+0x292/0x3f0 net/sctp/sm_sideeffect.c:406
call_timer_fn+0x228/0x820 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7ee/0xb70 kernel/time/timer.c:1666
run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
__do_softirq+0x2d7/0xb85 kernel/softirq.c:285
run_ksoftirqd+0x86/0x100 kernel/softirq.c:666
smpboot_thread_fn+0x450/0x7c0 kernel/smpboot.c:164
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
Code: 45 31 da 44 29 d0 41 89 c3 44 89 d0 41 01 da c1 c0 06 44 31 d8 29 c3
41 89 db 89 c3 44 01 d0 c1 c3 08 44 31 db 41 89 db 41 29 da <01> c3 41 c1
c3 10 45 31 da 45 89 d3 44 29 d0 41 01 da 41 c1 cb


---
This bug is generated by a dumb bot. It may contain errors.
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Direct all questions to syzk...@googlegroups.com.

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[Dmitry Vyukov]

On Mon, Mar 19, 2018 at 9:31 AM, syzbot
<syzbot+a13db9...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> 8f5fd927c3a7576d57248a2d7a0861c3f2795973 (Fri Mar 16 20:37:42 2018 +0000)
> Merge tag 'for-4.16-rc5-tag' of
> git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.

Another hung task on rtnl_lock:

#syz dup: INFO: task hung in netdev_run_todo

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