INFO: task hung in slip_close

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 811218ec Linux 4.19.172
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13ee3618d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c1cb1d27398c8808
dashboard link: https://syzkaller.appspot.com/bug?extid=2ae413c871540d6f94b2

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+2ae413...@syzkaller.appspotmail.com

INFO: task syz-executor.5:22213 blocked for more than 140 seconds.
Not tainted 4.19.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D27552 22213 8116 0x80000002
Call Trace:
context_switch syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:3517
schedule+0x8d/0x1b0 syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:3561
schedule_preempt_disabled+0xf/0x20 syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:3619
__mutex_lock_common syzkaller/managers/linux-4-19/kernel/kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 syzkaller/managers/linux-4-19/kernel/kernel/locking/mutex.c:1072
unregister_netdev+0xe/0x20 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:9337
slip_close+0x161/0x1c0 syzkaller/managers/linux-4-19/kernel/drivers/net/slip/slip.c:908
tty_ldisc_close+0xa2/0xd0 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:493
tty_ldisc_kill syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:639 [inline]
tty_ldisc_release+0xf5/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:806
tty_release_struct+0x20/0xe0 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_io.c:1611
tty_release+0xc70/0x1210 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_io.c:1784
__fput+0x2ce/0x890 syzkaller/managers/linux-4-19/kernel/fs/file_table.c:278
task_work_run+0x148/0x1c0 syzkaller/managers/linux-4-19/kernel/kernel/task_work.c:113
exit_task_work syzkaller/managers/linux-4-19/kernel/./include/linux/task_work.h:22 [inline]
do_exit+0xbf3/0x2be0 syzkaller/managers/linux-4-19/kernel/kernel/exit.c:870
do_group_exit+0x125/0x310 syzkaller/managers/linux-4-19/kernel/kernel/exit.c:967
get_signal+0x3f2/0x1f70 syzkaller/managers/linux-4-19/kernel/kernel/signal.c:2589
do_signal+0x8f/0x1670 syzkaller/managers/linux-4-19/kernel/arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x204/0x2a0 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:163
prepare_exit_to_usermode syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x465b09
Code: Bad RIP value.
RSP: 002b:00007fafe09b5218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000056bf68 RCX: 0000000000465b09
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf68
RBP: 000000000056bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf6c
R13: 00007ffe5afc6edf R14: 00007fafe09b5300 R15: 0000000000022000
INFO: task syz-executor.5:22256 blocked for more than 140 seconds.
Not tainted 4.19.172-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D27448 22256 8116 0x80000002
Call Trace:
context_switch syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:3517
schedule+0x8d/0x1b0 syzkaller/managers/linux-4-19/kernel/kernel/sched/core.c:3561
schedule_timeout+0x92d/0xfe0 syzkaller/managers/linux-4-19/kernel/kernel/time/timer.c:1794
do_wait_for_common syzkaller/managers/linux-4-19/kernel/kernel/sched/completion.c:83 [inline]
__wait_for_common syzkaller/managers/linux-4-19/kernel/kernel/sched/completion.c:104 [inline]
wait_for_common+0x29c/0x470 syzkaller/managers/linux-4-19/kernel/kernel/sched/completion.c:115
__flush_work+0x4bb/0x8b0 syzkaller/managers/linux-4-19/kernel/kernel/workqueue.c:2928
flush_all_backlogs syzkaller/managers/linux-4-19/kernel/net/core/dev.c:5283 [inline]
rollback_registered_many+0x4b1/0xe70 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:8173
rollback_registered+0xe9/0x1b0 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:8230
unregister_netdevice_queue+0x1de/0x3e0 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:9297
unregister_netdevice syzkaller/managers/linux-4-19/kernel/./include/linux/netdevice.h:2614 [inline]
unregister_netdev+0x18/0x20 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:9338
slip_close+0x161/0x1c0 syzkaller/managers/linux-4-19/kernel/drivers/net/slip/slip.c:908
tty_ldisc_close+0xa2/0xd0 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:493
tty_ldisc_kill syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:639 [inline]
tty_ldisc_release+0xf5/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:806
tty_release_struct+0x20/0xe0 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_io.c:1611
tty_release+0xc70/0x1210 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_io.c:1784
__fput+0x2ce/0x890 syzkaller/managers/linux-4-19/kernel/fs/file_table.c:278
task_work_run+0x148/0x1c0 syzkaller/managers/linux-4-19/kernel/kernel/task_work.c:113
exit_task_work syzkaller/managers/linux-4-19/kernel/./include/linux/task_work.h:22 [inline]
do_exit+0xbf3/0x2be0 syzkaller/managers/linux-4-19/kernel/kernel/exit.c:870
do_group_exit+0x125/0x310 syzkaller/managers/linux-4-19/kernel/kernel/exit.c:967
get_signal+0x3f2/0x1f70 syzkaller/managers/linux-4-19/kernel/kernel/signal.c:2589
do_signal+0x8f/0x1670 syzkaller/managers/linux-4-19/kernel/arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x204/0x2a0 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:163
prepare_exit_to_usermode syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x465b09
Code: Bad RIP value.
RSP: 002b:00007fafe09b5218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000056bf68 RCX: 0000000000465b09
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056bf68
RBP: 000000000056bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf6c
R13: 00007ffe5afc6edf R14: 00007fafe09b5300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1567:
#0: 000000001b9c518a (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 syzkaller/managers/linux-4-19/kernel/kernel/locking/lockdep.c:4440
1 lock held by in:imklog/7794:
#0: 000000001282abd6 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 syzkaller/managers/linux-4-19/kernel/fs/file.c:767
3 locks held by syz-executor.5/22213:
#0: 0000000019d86815 (&tty->ldisc_sem){++++}, at: __tty_ldisc_lock syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:320 [inline]
#0: 0000000019d86815 (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair_timeout syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:376 [inline]
#0: 0000000019d86815 (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:397 [inline]
#0: 0000000019d86815 (&tty->ldisc_sem){++++}, at: tty_ldisc_release+0x240/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:805
#1: 000000003684638c (&tty->ldisc_sem/1){+.+.}, at: __tty_ldisc_lock_nested syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:326 [inline]
#1: 000000003684638c (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair_timeout syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:378 [inline]
#1: 000000003684638c (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:397 [inline]
#1: 000000003684638c (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_release+0x354/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:805
#2: 00000000eb219894 (rtnl_mutex){+.+.}, at: unregister_netdev+0xe/0x20 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:9337
4 locks held by syz-executor.5/22256:
#0: 00000000e45365ab (&tty->ldisc_sem){++++}, at: __tty_ldisc_lock syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:320 [inline]
#0: 00000000e45365ab (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair_timeout syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:376 [inline]
#0: 00000000e45365ab (&tty->ldisc_sem){++++}, at: tty_ldisc_lock_pair syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:397 [inline]
#0: 00000000e45365ab (&tty->ldisc_sem){++++}, at: tty_ldisc_release+0x240/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:805
#1: 0000000076112790 (&tty->ldisc_sem/1){+.+.}, at: __tty_ldisc_lock_nested syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:326 [inline]
#1: 0000000076112790 (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair_timeout syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:378 [inline]
#1: 0000000076112790 (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_lock_pair syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:397 [inline]
#1: 0000000076112790 (&tty->ldisc_sem/1){+.+.}, at: tty_ldisc_release+0x354/0x440 syzkaller/managers/linux-4-19/kernel/drivers/tty/tty_ldisc.c:805
#2: 00000000eb219894 (rtnl_mutex){+.+.}, at: unregister_netdev+0xe/0x20 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:9337
#3: 000000009241a1b5 (cpu_hotplug_lock.rw_sem){++++}, at: get_online_cpus syzkaller/managers/linux-4-19/kernel/./include/linux/cpu.h:137 [inline]
#3: 000000009241a1b5 (cpu_hotplug_lock.rw_sem){++++}, at: flush_all_backlogs syzkaller/managers/linux-4-19/kernel/net/core/dev.c:5276 [inline]
#3: 000000009241a1b5 (cpu_hotplug_lock.rw_sem){++++}, at: rollback_registered_many+0x3a8/0xe70 syzkaller/managers/linux-4-19/kernel/net/core/dev.c:8173
3 locks held by kworker/0:0/2247:
#0: 0000000061e3b4db ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: process_one_work+0x767/0x1570 syzkaller/managers/linux-4-19/kernel/kernel/workqueue.c:2126
#1: 000000003500e0e5 ((addr_chk_work).work){+.+.}, at: process_one_work+0x79c/0x1570 syzkaller/managers/linux-4-19/kernel/kernel/workqueue.c:2130
#2: 00000000eb219894 (rtnl_mutex){+.+.}, at: addrconf_verify_work+0xa/0x20 syzkaller/managers/linux-4-19/kernel/net/ipv6/addrconf.c:4476
1 lock held by syz-executor.5/31630:

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

NMI backtrace for cpu 0
CPU: 0 PID: 1567 Comm: khungtaskd Not tainted 4.19.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack syzkaller/managers/linux-4-19/kernel/lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef syzkaller/managers/linux-4-19/kernel/lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 syzkaller/managers/linux-4-19/kernel/lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1f0 syzkaller/managers/linux-4-19/kernel/lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace syzkaller/managers/linux-4-19/kernel/./include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks syzkaller/managers/linux-4-19/kernel/kernel/hung_task.c:203 [inline]
watchdog+0x991/0xe60 syzkaller/managers/linux-4-19/kernel/kernel/hung_task.c:287
kthread+0x33f/0x460 syzkaller/managers/linux-4-19/kernel/kernel/kthread.c:259
ret_from_fork+0x24/0x30 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 31630 Comm: syz-executor.5 Not tainted 4.19.172-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:mddev_find+0x3f/0x770 syzkaller/managers/linux-4-19/kernel/drivers/md/md.c:588
Code: 31 ff 89 de e8 92 f6 ab fb 85 db 74 3f e8 19 f5 ab fb 89 d8 bf 09 00 00 00 c1 e8 14 41 89 c6 89 c6 89 44 24 08 e8 71 f6 ab fb <41> 83 fe 09 0f 84 97 02 00 00 e8 f2 f4 ab fb 83 e3 c0 89 d8 c1 e8
RSP: 0018:ffff88804c7ef7c0 EFLAGS: 00000297
RAX: 0000000000000002 RBX: 0000000000900000 RCX: ffffffff85b664bf
RDX: 0000000000000009 RSI: ffff88804bb04500 RDI: 0000000000000005
RBP: ffff8880ab46b180 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000005 R11: 0000000000000000 R12: ffff8880ab46b180
R13: ffff8880ab46b250 R14: 0000000000000009 R15: ffff8880ab46b198
FS: 00007fafe09b5700(0000) GS:ffff8880ba100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ef3f000 CR3: 000000008f596000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
md_open+0x3a/0x2a0 syzkaller/managers/linux-4-19/kernel/drivers/md/md.c:7448
__blkdev_get+0x372/0x1480 syzkaller/managers/linux-4-19/kernel/fs/block_dev.c:1494
blkdev_get+0xb0/0x940 syzkaller/managers/linux-4-19/kernel/fs/block_dev.c:1627
blkdev_open+0x202/0x290 syzkaller/managers/linux-4-19/kernel/fs/block_dev.c:1788
do_dentry_open+0x4aa/0x1160 syzkaller/managers/linux-4-19/kernel/fs/open.c:796
do_last syzkaller/managers/linux-4-19/kernel/fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 syzkaller/managers/linux-4-19/kernel/fs/namei.c:3537
do_filp_open+0x18c/0x3f0 syzkaller/managers/linux-4-19/kernel/fs/namei.c:3567
do_sys_open+0x3b3/0x520 syzkaller/managers/linux-4-19/kernel/fs/open.c:1085
do_syscall_64+0xf9/0x620 syzkaller/managers/linux-4-19/kernel/arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x465b09
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fafe09b5188 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: ffffffffffffff9c
RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffe5afc6edf R14: 00007fafe09b5300 R15: 0000000000022000


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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