INFO: rcu detected stall in pfkey_sendmsg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    a26d94bff4d5 net: bridge: remove unneeded variable 'err'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14c7a4cd400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
dashboard link: https://syzkaller.appspot.com/bug?extid=e1d3a7522b4d05aeede4
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+e1d3a7522b4d05aeede4@xxxxxxxxxxxxxxxxxxxxxxxxx

ip6_tunnel: ip6tnl1 xmit: Local address not yet configured!
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=9e6/1/0x4000000000000002  
softirq=418161/418162 fqs=5249
rcu: 	 (t=10502 jiffies g=488537 q=1706)
NMI backtrace for cpu 1
CPU: 1 PID: 18240 Comm: syz-executor3 Not tainted 4.20.0-rc6+ #352
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+0x244/0x39d lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.2+0x5c/0xa1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1e8/0x22a 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:164 [inline]
 rcu_dump_cpu_stacks+0x16f/0x1bc kernel/rcu/tree.c:1195
 print_cpu_stall.cold.67+0x1f3/0x3c7 kernel/rcu/tree.c:1334
 check_cpu_stall kernel/rcu/tree.c:1408 [inline]
 rcu_pending kernel/rcu/tree.c:2961 [inline]
 rcu_check_callbacks+0xf3b/0x13f0 kernel/rcu/tree.c:2506
 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:1034 [inline]
 smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1059
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:__read_once_size include/linux/compiler.h:182 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:69 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x20/0x50 kernel/kcov.c:101
Code: 4c d8 20 4c 89 08 5d c3 66 90 55 48 89 e5 48 8b 75 08 65 48 8b 04 25  
40 ee 01 00 65 8b 15 28 69 82 7e 81 e2 00 01 1f 00 75 2b <8b> 90 d8 12 00  
00 83 fa 02 75 20 48 8b 88 e0 12 00 00 8b 80 dc 12
RSP: 0018:ffff888197daf338 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8881d207c040 RBX: ffff8881c39fd688 RCX: ffffc9000be34000
RDX: 0000000000000000 RSI: ffffffff86cdda27 RDI: ffff8881c39fd688
RBP: ffff888197daf338 R08: ffff8881d207c040 R09: 0000000000000008
R10: 0000000000000003 R11: ffff8881d207c040 R12: dffffc0000000000
R13: 0000000000000000 R14: 000000000000227d R15: 0000000000000000
 xfrm_policy_insert_list+0x257/0x1020 net/xfrm/xfrm_policy.c:1531
 xfrm_policy_inexact_insert+0x166/0xee0 net/xfrm/xfrm_policy.c:1195
 xfrm_policy_insert+0x639/0x850 net/xfrm/xfrm_policy.c:1570
 pfkey_spdadd+0x10f8/0x19d0 net/key/af_key.c:2339
 pfkey_process+0x857/0x9a0 net/key/af_key.c:2844
 pfkey_sendmsg+0x5e5/0xfb0 net/key/af_key.c:3683
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:631
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
 __sys_sendmsg+0x11d/0x280 net/socket.c:2154
 __do_sys_sendmsg net/socket.c:2163 [inline]
 __se_sys_sendmsg net/socket.c:2161 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007efc20b07c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007efc20b086d4
R13: 00000000004c443a R14: 00000000004d7410 R15: 00000000ffffffff


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