INFO: task hung in ip6gre_exit_batch_net (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: daefdc9e Linux 4.19.161
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15eb9123500000
kernel config: https://syzkaller.appspot.com/x/.config?x=5e8be1f59358cc24
dashboard link: https://syzkaller.appspot.com/bug?extid=596449fca0c48352d1f4
compiler: gcc (GCC) 10.1.0-syz 20200507

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+596449...@syzkaller.appspotmail.com

Bluetooth: hci1: command 0x0406 tx timeout
Bluetooth: hci2: command 0x0406 tx timeout
Bluetooth: hci3: command 0x0406 tx timeout
Bluetooth: hci5: command 0x0406 tx timeout
Bluetooth: hci4: command 0x0406 tx timeout
INFO: task kworker/u4:1:23 blocked for more than 140 seconds.
Not tainted 4.19.161-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1 D25992 23 2 0x80000000
Workqueue: netns cleanup_net
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
ip6gre_exit_batch_net+0x82/0x6c0 net/ipv6/ip6_gre.c:1624
ops_exit_list+0xf9/0x150 net/core/net_namespace.c:156
cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:553
process_one_work+0x864/0x1570 kernel/workqueue.c:2155
worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
INFO: task syz-executor.1:12547 blocked for more than 140 seconds.
Not tainted 4.19.161-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D29024 12547 8142 0x80000004
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
exp_funnel_lock kernel/rcu/tree_exp.h:320 [inline]
_synchronize_rcu_expedited+0x60c/0x6f0 kernel/rcu/tree_exp.h:667
synchronize_rcu+0xc6/0x160 kernel/rcu/tree_plugin.h:818
cfcnfg_remove+0x2b/0x8f net/caif/cfcnfg.c:121
caif_exit_net+0x34d/0x450 net/caif/caif_dev.c:538
ops_exit_list+0xa5/0x150 net/core/net_namespace.c:153
setup_net+0x3d1/0x720 net/core/net_namespace.c:332
copy_net_ns+0x1f7/0x335 net/core/net_namespace.c:438
create_new_namespaces+0x3f6/0x7b0 kernel/nsproxy.c:107
unshare_nsproxy_namespaces+0xbd/0x1f0 kernel/nsproxy.c:206
ksys_unshare+0x36c/0x9a0 kernel/fork.c:2551
__do_sys_unshare kernel/fork.c:2619 [inline]
__se_sys_unshare kernel/fork.c:2617 [inline]
__x64_sys_unshare+0x2d/0x40 kernel/fork.c:2617
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45e0f9
Code: 2a 03 00 00 48 83 ec 58 48 89 6c 24 50 48 8d 6c 24 50 8b 44 24 68 85 c0 0f 84 3a 02 00 00 48 8b 4c 24 60 48 8d 15 07 96 b0 00 <eb> 07 48 8b 92 c0 01 00 00 48 85 d2 0f 84 15 02 00 00 48 39 8a c8
RSP: 002b:00007fb85b653c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 000000000045e0f9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 000000000119c100 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c0dc
R13: 00007ffdf6acb49f R14: 00007fb85b6549c0 R15: 000000000119c0dc
INFO: task syz-executor.2:12592 blocked for more than 140 seconds.
Not tainted 4.19.161-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D28648 12592 8144 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3619
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
tun_detach drivers/net/tun.c:751 [inline]
tun_chr_close+0x3a/0x180 drivers/net/tun.c:3267
__fput+0x2ce/0x890 fs/file_table.c:278
task_work_run+0x148/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x417a51
Code: 24 48 8b 4c 24 40 48 89 4c 24 08 e8 29 f4 00 00 8b 44 24 18 8b 4c 24 1c 39 c8 75 22 48 8b 44 24 38 48 89 04 24 e8 1f 33 ff ff <8b> 44 24 18 8b 4c 24 1c 39 c8 48 8b 44 24 40 e9 5a ff ff ff 48 8b
RSP: 002b:00007fffbc661810 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000417a51
RDX: 0000000000000000 RSI: ffffffff88158bd8 RDI: 0000000000000005
RBP: 0000000000000001 R08: ffffffff8100432f R09: 0000000030ea99eb
R10: 0000000030ea99ef R11: 0000000000000293 R12: 000000000119ca00
R13: 000000000119ca00 R14: 00000000000003e8 R15: 000000000119c034

Showing all locks held in the system:
4 locks held by kworker/u4:1/23:
#0: 00000000ac5e79ae ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2126
#1: 000000004c247ca4 (net_cleanup_work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2130
#2: 000000008baa0333 (pernet_ops_rwsem){++++}, at: cleanup_net+0xa8/0x8b0 net/core/net_namespace.c:520
#3: 00000000b088fae5 (rtnl_mutex){+.+.}, at: ip6gre_exit_batch_net+0x82/0x6c0 net/ipv6/ip6_gre.c:1624
1 lock held by khungtaskd/1566:
#0: 00000000d670c100 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
3 locks held by kworker/0:2/3670:
#0: 00000000a5098d7f ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2126
#1: 000000009ba5ba0f ((addr_chk_work).work){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2130
#2: 00000000b088fae5 (rtnl_mutex){+.+.}, at: addrconf_verify_work+0xa/0x20 net/ipv6/addrconf.c:4475
3 locks held by syz-executor.1/12547:
#0: 000000008baa0333 (pernet_ops_rwsem){++++}, at: copy_net_ns+0x1d8/0x335 net/core/net_namespace.c:434
#1: 00000000b088fae5 (rtnl_mutex){+.+.}, at: caif_exit_net+0x38/0x450 net/caif/caif_dev.c:517
#2: 000000002bc8f7e8 (&caifn->caifdevs.lock){+.+.}, at: caif_exit_net+0x4f/0x450 net/caif/caif_dev.c:518
1 lock held by syz-executor.2/12592:
#0: 00000000b088fae5 (rtnl_mutex){+.+.}, at: tun_detach drivers/net/tun.c:751 [inline]
#0: 00000000b088fae5 (rtnl_mutex){+.+.}, at: tun_chr_close+0x3a/0x180 drivers/net/tun.c:3267

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

NMI backtrace for cpu 0
CPU: 0 PID: 1566 Comm: khungtaskd Not tainted 4.19.161-syzkaller #0
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+0x1fc/0x2fe lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x991/0xe60 kernel/hung_task.c:287
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60


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[syzbot]

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