INFO: rcu detected stall in cleanup_net (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: fb1c592cf4c9 Merge tag 'char-misc-4.19-rc7' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=157bc406400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0af03fe452b65fb
dashboard link: https://syzkaller.appspot.com/bug?extid=09fbf18d171bd0dfd878
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [fred...@kernel.org linux-...@vger.kernel.org
mi...@kernel.org tg...@linutronix.de]

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+09fbf1...@syzkaller.appspotmail.com

rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
rcu: (detected by 1, t=10502 jiffies, g=28405, q=1)
rcu: All QSes seen, last rcu_sched kthread activity 10502
(4295000730-4294990228), jiffies_till_next_fqs=1, root ->qsmask 0x0
kworker/u4:2 R running task 14704 30 2 0x80000008
Workqueue: netns cleanup_net
Call Trace:
<IRQ>
sched_show_task.cold.83+0x2b6/0x30a kernel/sched/core.c:5296
print_other_cpu_stall.cold.79+0xa83/0xba5 kernel/rcu/tree.c:1430
check_cpu_stall kernel/rcu/tree.c:1557 [inline]
__rcu_pending kernel/rcu/tree.c:3276 [inline]
rcu_pending kernel/rcu/tree.c:3319 [inline]
rcu_check_callbacks+0xafc/0x1990 kernel/rcu/tree.c:2665
update_process_times+0x2d/0x70 kernel/time/timer.c:1636
tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1029 [inline]
smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1054
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
</IRQ>
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:69 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x26/0x50 kernel/kcov.c:101
Code: 5d c3 66 90 55 48 89 e5 65 48 8b 04 25 40 ee 01 00 65 8b 15 2c 18 83
7e 81 e2 00 01 1f 00 48 8b 75 08 75 2b 8b 90 d0 12 00 00 <83> fa 02 75 20
48 8b 88 d8 12 00 00 8b 80 d4 12 00 00 48 8b 11 48
RSP: 0018:ffff8801d951f190 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8801d952c080 RBX: ffff8801d951f218 RCX: ffffffff81728a89
RDX: 0000000000000000 RSI: ffffffff81728a38 RDI: 0000000000000005
RBP: ffff8801d951f190 R08: ffff8801d952c080 R09: ffffed003b5c5ba0
R10: ffffed003b5c5ba0 R11: ffff8801dae2dd07 R12: ffffed003b2a3e50
R13: 1ffff1003b2a3e3c R14: dffffc0000000000 R15: 0000000000000001
rep_nop arch/x86/include/asm/processor.h:665 [inline]
cpu_relax arch/x86/include/asm/processor.h:670 [inline]
csd_lock_wait kernel/smp.c:108 [inline]
smp_call_function_single+0x258/0x660 kernel/smp.c:302
_rcu_barrier+0x462/0x790 kernel/rcu/tree.c:3462
rcu_barrier+0x10/0x20 kernel/rcu/tree_plugin.h:834
cleanup_net+0x641/0xb10 net/core/net_namespace.c:562
process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
rcu: rcu_sched kthread starved for 10502 jiffies! g28405 f0x2
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_sched R running task 23272 11 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
schedule+0xfe/0x460 kernel/sched/core.c:3517
schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
rcu_gp_kthread+0x9d9/0x2310 kernel/rcu/tree.c:2194
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (0 ticks this GP) idle=84a/1/0x4000000000000000
softirq=91676/91676 fqs=0
rcu: (detected by 1, t=10623 jiffies, g=85357, q=163)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 9148 Comm: syz-executor1 Not tainted 4.19.0-rc6+ #51
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:vmx_complete_atomic_exit arch/x86/kvm/vmx.c:10409 [inline]
RIP: 0010:vmx_vcpu_run+0x1e47/0x289d arch/x86/kvm/vmx.c:10927
Code: ff 00 02 00 80 0f 85 c1 01 00 00 e8 13 9e 5d 00 48 c7 c7 60 c5 03 88
e8 77 13 6c 02 48 8b 04 24 65 48 89 05 3b 99 e0 7e cd 02 <48> c7 c7 60 c5
03 88 e8 5d 13 6c 02 48 89 da 48 b8 00 00 00 00 00
RSP: 0018:ffff8801c5227370 EFLAGS: 00000092
RAX: ffff8801c6dd95c0 RBX: ffff8801c6ddecd0 RCX: ffffc90003ef8000
RDX: 00000000000028be RSI: ffffffff838d4928 RDI: 0000000000000005
RBP: ffff8801c5227840 R08: ffff8801cbe9a480 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000080000202
R13: 0000000000000000 R14: 0000000080000202 R15: 0000000080000200
FS: 00007fda28f8f700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001ce251000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
vcpu_run arch/x86/kvm/x86.c:7730 [inline]
kvm_arch_vcpu_ioctl_run+0x375/0x16e0 arch/x86/kvm/x86.c:7930
kvm_vcpu_ioctl+0x72b/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2590
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457579
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fda28f8ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457579
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fda28f8f6d4
R13: 00000000004c003b R14: 00000000004d0108 R15: 00000000ffffffff
rcu: rcu_preempt kthread starved for 10623 jiffies! g85357 f0x0
RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 23272 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
schedule+0xfe/0x460 kernel/sched/core.c:3517
schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
rcu_gp_kthread+0x9d9/0x2310 kernel/rcu/tree.c:2194
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
__ntfs_error: 4 callbacks suppressed
ntfs: (device loop3): ntfs_fill_super(): Unable to determine device size.
overlayfs: failed to resolve './fi0e1': -2
overlayfs: failed to resolve './fi0e1': -2


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[syzbot]

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