INFO: rcu detected stall in _decode_session6

[syzbot]

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.

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Reported-by: syzbot+24d1c1...@syzkaller.appspotmail.com
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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


---
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[Dmitry Vyukov]

On Mon, Feb 12, 2018 at 4:23 PM, syzbot
<syzbot+24d1c1...@syzkaller.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

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