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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 12 Feb 2018 16:26:55 +0100
Message-ID: <CACT4Y+Z-iMWQccvthBAb2Ze4GjkVAm-B7m=b+KYg8AqEn4gw1Q@mail.gmail.com>
Subject: Re: INFO: rcu detected stall in xfrm_confirm_neigh
To:     syzbot <syzbot+7d03c810e50aaedef98a@syzkaller.appspotmail.com>
Cc:     babu.moger@oracle.com, dzickus@redhat.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, npiggin@gmail.com,
        Philippe Ombredanne <pombredanne@nexb.com>,
        syzkaller-bugs@googlegroups.com,
        Thomas Gleixner <tglx@linutronix.de>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        David Miller <davem@davemloft.net>,
        netdev <netdev@vger.kernel.org>
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On Mon, Feb 12, 2018 at 4:23 PM, syzbot
<syzbot+7d03c810e50aaedef98a@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on net-next commit
> 9515a2e082f91457db0ecff4b65371d0fb5d9aad (Thu Jan 25 03:37:38 2018 +0000)
> net/ipv4: Allow send to local broadcast from a socket bound to a VRF
>
> So far this crash happened 6 times on net-next.
> 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


> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7d03c810e50aaedef98a@syzkaller.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-...!: (124998 ticks this GP) idle=376/140000000000001/0
> softirq=506054/506054 fqs=19
>          (t=125000 jiffies g=289415 c=289414 q=312)
> rcu_sched kthread starved for 124920 jiffies! g289415 c289414 f0x0
> RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0
> rcu_sched       R  running task    23456     8      2 0x80000000
> Call Trace:
>  context_switch kernel/sched/core.c:2799 [inline]
>  __schedule+0x8eb/0x2060 kernel/sched/core.c:3375
>  schedule+0xf5/0x430 kernel/sched/core.c:3434
>  schedule_timeout+0x118/0x230 kernel/time/timer.c:1793
>  rcu_gp_kthread+0x9e5/0x1930 kernel/rcu/tree.c:2314
>  kthread+0x33c/0x400 kernel/kthread.c:238
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541
> NMI backtrace for cpu 1
> CPU: 1 PID: 15893 Comm: syz-executor0 Not tainted 4.15.0-rc9+ #210
> 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:1628
>  tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
>  tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
>  __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:937
>  </IRQ>
> RIP: 0010:__read_once_size include/linux/compiler.h:183 [inline]
> RIP: 0010:__sanitizer_cov_trace_pc+0x3b/0x50 kernel/kcov.c:106
> RSP: 0018:ffff8801a6867820 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
> RAX: 0000000000010000 RBX: ffff8801caf7d200 RCX: ffffffff84acc87d
> RDX: 000000000000ffff RSI: ffffc90002aa6000 RDI: ffff8801c54c4f50
> RBP: ffff8801a6867820 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c54c4e00
> R13: dffffc0000000000 R14: ffffed00395efa5f R15: ffff8801caf7d2fc
>  xfrm_get_dst_nexthop net/xfrm/xfrm_policy.c:2732 [inline]
>  xfrm_confirm_neigh+0xad/0x270 net/xfrm/xfrm_policy.c:2759
>  dst_confirm_neigh include/net/dst.h:419 [inline]
>  raw_sendmsg+0xece/0x23b0 net/ipv4/raw.c:702
>  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:764
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:640
>  SYSC_sendto+0x361/0x5c0 net/socket.c:1747
>  SyS_sendto+0x40/0x50 net/socket.c:1715
>  entry_SYSCALL_64_fastpath+0x29/0xa0
> RIP: 0033:0x452f19
> RSP: 002b:00007f00a389ec58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000452f19
> RDX: 000000000000001e RSI: 0000000020098000 RDI: 0000000000000013
> RBP: 0000000000000510 R08: 0000000020cf9000 R09: 0000000000000010
> R10: fffffffffffffffe R11: 0000000000000212 R12: 00000000006f6a20
> R13: 00000000ffffffff R14: 00007f00a389f6d4 R15: 0000000000000001
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
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>
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