INFO: rcu detected stall in pppol2tp_sendmsg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: ee809c7e Linux 4.19.72
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15785c95600000
kernel config: https://syzkaller.appspot.com/x/.config?x=ad6c5c98f4231da9
dashboard link: https://syzkaller.appspot.com/bug?extid=86d03bd8194375ebb2d9
compiler: gcc (GCC) 9.0.0 20181231 (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+86d03b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=642/1/0x4000000000000002
softirq=99428/99429 fqs=5250
rcu: (t=10502 jiffies g=141669 q=579)
NMI backtrace for cpu 0
CPU: 0 PID: 31134 Comm: syz-executor.2 Not tainted 4.19.72 #0
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+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 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+0x189/0x1d5 kernel/rcu/tree.c:1340
print_cpu_stall kernel/rcu/tree.c:1478 [inline]
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3293 [inline]
rcu_pending kernel/rcu/tree.c:3336 [inline]
rcu_check_callbacks.cold+0x5e3/0xd90 kernel/rcu/tree.c:2682
update_process_times+0x32/0x80 kernel/time/timer.c:1636
tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:164
tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x33b/0xdc0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline]
smp_apic_timer_interrupt+0x111/0x550 arch/x86/kernel/apic/apic.c:1092
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789
[inline]
RIP: 0010:lock_is_held_type+0x17e/0x210 kernel/locking/lockdep.c:3940
Code: 00 00 00 fc ff df 41 c7 85 7c 08 00 00 00 00 00 00 48 c1 e8 03 80 3c
10 00 75 63 48 83 3d e1 82 20 07 00 74 30 48 89 df 57 9d <0f> 1f 44 00 00
48 83 c4 08 44 89 e0 5b 41 5c 41 5d 5d c3 48 83 c4
RSP: 0018:ffff888069507458 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff10e48c1 RBX: 0000000000000282 RCX: ffff88805cecc980
RDX: dffffc0000000000 RSI: ffffffff8879f320 RDI: 0000000000000282
RBP: ffff888069507478 R08: ffff88805cecc100 R09: ffffed1015d04733
R10: ffffed1015d04732 R11: ffff8880ae823993 R12: 0000000000000001
R13: ffff88805cecc100 R14: ffff888069507840 R15: 0000000000000000
lock_is_held include/linux/lockdep.h:344 [inline]
rcu_read_lock_held kernel/rcu/update.c:287 [inline]
rcu_read_lock_held+0xa3/0xd0 kernel/rcu/update.c:279
xfrm_sk_policy_lookup+0x329/0x510 net/xfrm/xfrm_policy.c:1186
xfrm_lookup_with_ifid+0x1de/0x1cb0 net/xfrm/xfrm_policy.c:2066
xfrm_lookup net/xfrm/xfrm_policy.c:2203 [inline]
xfrm_lookup_route+0x3b/0x1f0 net/xfrm/xfrm_policy.c:2214
ip6_dst_lookup_flow+0x189/0x220 net/ipv6/ip6_output.c:1086
inet6_csk_route_socket+0x854/0xe70 net/ipv6/inet6_connection_sock.c:110
inet6_csk_xmit+0x110/0x5ba net/ipv6/inet6_connection_sock.c:125
l2tp_xmit_core net/l2tp/l2tp_core.c:1033 [inline]
l2tp_xmit_skb+0x116c/0x1460 net/l2tp/l2tp_core.c:1135
pppol2tp_sendmsg+0x4a2/0x6b0 net/l2tp/l2tp_ppp.c:329
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:632
___sys_sendmsg+0x3e2/0x920 net/socket.c:2115
__sys_sendmmsg+0x1bf/0x4e0 net/socket.c:2210
__do_sys_sendmmsg net/socket.c:2239 [inline]
__se_sys_sendmmsg net/socket.c:2236 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2236
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4598e9
Code: fd b7 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 b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f144957bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00000000004598e9
RDX: 000000000400023a RSI: 0000000020005fc0 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f144957c6d4
R13: 00000000004c70a7 R14: 00000000004dc768 R15: 00000000ffffffff


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.