Date:   Mon, 12 Feb 2018 16:26:12 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+24d1c14022d23c04a83e@...kaller.appspotmail.com>
Cc:     babu.moger@...cle.com, dzickus@...hat.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, npiggin@...il.com,
        syzkaller-bugs@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: INFO: rcu detected stall in _decode_session6

On Mon, Feb 12, 2018 at 4:23 PM, syzbot
<syzbot+24d1c14022d23c04a83e@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on net-next commit
> d0adb51edb73c94a595bfa9d9bd8b35977e74fbf
>
> 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.


+xfrm maintainers

#syz dup: INFO: rcu detected stall in __xfrm_decode_session


> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+24d1c14022d23c04a83e@...kaller.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: rcu_sched self-detected stall on CPU
>         1-....: (1 GPs behind) idle=41e/140000000000001/0
> softirq=91762/91764 fqs=31218
>          (t=125000 jiffies g=53093 c=53092 q=1018)
> NMI backtrace for cpu 1
> CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 4.15.0-rc5+ #177
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x122/0x180 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+0x186/0x1d9 kernel/rcu/tree.c:1459
>  print_cpu_stall kernel/rcu/tree.c:1608 [inline]
>  check_cpu_stall.isra.61+0xbb8/0x15b0 kernel/rcu/tree.c:1676
>  __rcu_pending kernel/rcu/tree.c:3440 [inline]
>  rcu_pending kernel/rcu/tree.c:3502 [inline]
>  rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
>  update_process_times+0x30/0x60 kernel/time/timer.c:1630
>  tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
>  tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1166
>  __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
>  __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275
>  hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309
>  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
>  smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
>  apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:904
>  </IRQ>
> RIP: 0010:__sanitizer_cov_trace_pc+0x1e/0x50 kernel/kcov.c:97
> RSP: 0018:ffff8801d9fae2f8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff11
> RAX: ffff8801d9f9e440 RBX: ffff8801c3591340 RCX: ffffffff84c2553b
> RDX: 0000000000000100 RSI: ffff8801b06a0640 RDI: 0000000000000000
> RBP: ffff8801d9fae2f8 R08: ffffed00360d6059 R09: ffffed00360d6059
> R10: 000000000000000b R11: ffffed00360d6058 R12: ffff8801b06a0658
> R13: ffff8801d9fae498 R14: 00000000000025c0 R15: dffffc0000000000
>  _decode_session6+0x9eb/0x1380 net/ipv6/xfrm6_policy.c:160
>  __xfrm_decode_session+0x68/0x110 net/xfrm/xfrm_policy.c:2358
>  xfrm_decode_session_reverse include/net/xfrm.h:1213 [inline]
>  icmpv6_route_lookup+0x356/0x660 net/ipv6/icmp.c:372
>  icmp6_send+0x17cd/0x28c0 net/ipv6/icmp.c:551
>  icmpv6_param_prob+0x2c/0x40 net/ipv6/icmp.c:598
>  ipv6_frag_rcv+0x342b/0x5320 net/ipv6/reassembly.c:583
>  ip6_input_finish+0x37e/0x17a0 net/ipv6/ip6_input.c:284
>  NF_HOOK include/linux/netfilter.h:250 [inline]
>  ip6_input+0xe9/0x560 net/ipv6/ip6_input.c:327
>  dst_input include/net/dst.h:449 [inline]
>  ip6_rcv_finish+0x1a9/0x7a0 net/ipv6/ip6_input.c:71
>  NF_HOOK include/linux/netfilter.h:250 [inline]
>  ipv6_rcv+0xf37/0x1fa0 net/ipv6/ip6_input.c:208
>  __netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4499
>  __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4564
>  process_backlog+0x203/0x740 net/core/dev.c:5244
>  napi_poll net/core/dev.c:5642 [inline]
>  net_rx_action+0x792/0x1910 net/core/dev.c:5708
>  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
>  run_ksoftirqd+0x50/0x100 kernel/softirq.c:666
>  smpboot_thread_fn+0x450/0x7c0 kernel/smpboot.c:164
>  kthread+0x33c/0x400 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:515
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
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