INFO: rcu detected stall in sctp_packet_transmit

[syzbot <syzbot+ff0b569fb5111dcd1a36@syzkaller.appspotmail.com>]

Hello,

syzbot found the following crash on:

HEAD commit:    961423f9fcbc Merge branch 'sctp-Introduce-sctp_flush_ctx'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1366aea7800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=51fb0a6913f757db
dashboard link: https://syzkaller.appspot.com/bug?extid=ff0b569fb5111dcd1a36
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+ff0b569fb5111dcd1a36@syzkaller.appspotmail.com

INFO: rcu_sched self-detected stall on CPU
	0-....: (1 GPs behind) idle=dae/1/4611686018427387908 softirq=93090/93091  
fqs=30902
	 (t=125000 jiffies g=51107 c=51106 q=972)
NMI backtrace for cpu 0
CPU: 0 PID: 24668 Comm: syz-executor6 Not tainted 4.17.0-rc4+ #44
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __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_single_cpu_backtrace include/linux/nmi.h:156 [inline]
  rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1376
  print_cpu_stall kernel/rcu/tree.c:1525 [inline]
  check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593
  __rcu_pending kernel/rcu/tree.c:3356 [inline]
  rcu_pending kernel/rcu/tree.c:3401 [inline]
  rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763
  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+0x3e3/0x10a0 kernel/time/hrtimer.c:1460
  hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
  smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
RIP: 0010:sctp_v6_xmit+0x259/0x6b0 net/sctp/ipv6.c:219
RSP: 0018:ffff8801dae068e8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000007 RBX: ffff8801bb7ec800 RCX: ffffffff86f1b345
RDX: 0000000000000000 RSI: ffffffff86f1b381 RDI: ffff8801b73d97c4
RBP: ffff8801dae06988 R08: ffff88019505c300 R09: ffffed003b5c46c2
R10: ffffed003b5c46c2 R11: ffff8801dae23613 R12: ffff88011fd57300
R13: ffff8801bb7ecec8 R14: 0000000000000029 R15: 0000000000000002
  sctp_packet_transmit+0x26f6/0x3ba0 net/sctp/output.c:642
  sctp_outq_flush_transports net/sctp/outqueue.c:1164 [inline]
  sctp_outq_flush+0x5f5/0x3430 net/sctp/outqueue.c:1212
  sctp_outq_uncork+0x6a/0x80 net/sctp/outqueue.c:776
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1820 [inline]
  sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
  sctp_do_sm+0x596/0x7160 net/sctp/sm_sideeffect.c:1191
  sctp_generate_heartbeat_event+0x218/0x450 net/sctp/sm_sideeffect.c:406
  call_timer_fn+0x230/0x940 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0x79e/0xc50 kernel/time/timer.c:1666
  run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1d1/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:525 [inline]
  smp_apic_timer_interrupt+0x17e/0x710 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
  </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783  
[inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160  
[inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa1/0xc0  
kernel/locking/spinlock.c:184
RSP: 0018:ffff880196227328 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 0000000000000286 RCX: 0000000000000000
RDX: 1ffffffff11a316d RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff880196227338 R08: ffffed003b5c4b81 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801dae25c00
R13: ffff8801dae25c80 R14: ffff880196227758 R15: ffff8801dae25c00
  unlock_hrtimer_base kernel/time/hrtimer.c:887 [inline]
  hrtimer_start_range_ns+0x692/0xd10 kernel/time/hrtimer.c:1118
  hrtimer_start_expires include/linux/hrtimer.h:412 [inline]
  futex_wait_queue_me+0x304/0x820 kernel/futex.c:2517
  futex_wait+0x450/0x9f0 kernel/futex.c:2645
  do_futex+0x336/0x27d0 kernel/futex.c:3527
  __do_sys_futex kernel/futex.c:3587 [inline]
  __se_sys_futex kernel/futex.c:3555 [inline]
  __x64_sys_futex+0x46a/0x680 kernel/futex.c:3555
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a09
RSP: 002b:0000000000a3e938 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 0000000000045a9b RCX: 0000000000455a09
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072becc
RBP: 000000000072becc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000a3e940 R11: 0000000000000246 R12: 0000000000000019
R13: 0000000000000002 R14: 000000000072bea0 R15: 0000000000045a8f


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