INFO: rcu detected stall in x25_connect

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    38355a5f9a22 bnx2x: Fix NULL pointer dereference in bnx2x_..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=15fe1677400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a91d685acb971514
dashboard link: https://syzkaller.appspot.com/bug?extid=564c57b4bf1df3ce1c94
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+564c57b4bf1df3ce1c94@xxxxxxxxxxxxxxxxxxxxxxxxx

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 GPs behind) idle=b82/1/0x4000000000000002  
softirq=245727/245728 fqs=2
rcu: 	 (t=10500 jiffies g=375665 q=22)
rcu: rcu_preempt kthread starved for 10496 jiffies! g375665 f0x0  
RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I22568    10      2 0x80000000
Call Trace:
 context_switch kernel/sched/core.c:2831 [inline]
 __schedule+0x86c/0x1ed0 kernel/sched/core.c:3472
 schedule+0xfe/0x460 kernel/sched/core.c:3516
 schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
 rcu_gp_fqs_loop+0x762/0xa80 kernel/rcu/tree.c:1934
 rcu_gp_kthread+0x341/0xc70 kernel/rcu/tree.c:2090
 kthread+0x35a/0x440 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 1
CPU: 1 PID: 23613 Comm: syz-executor0 Not tainted 4.20.0-rc7+ #249
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+0x1d3/0x2c6 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.4+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1c2/0x22c 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.65+0x1f3/0x3c6 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+0xac1/0x1410 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:__x25_find_socket+0x6c/0x110 net/x25/af_x25.c:327
Code: 2f e8 d8 a9 87 fa 48 8d 7b 68 48 89 f8 48 c1 e8 03 42 80 3c 20 00 0f  
85 a1 00 00 00 48 8b 5b 68 48 85 db 74 7c e8 b4 a9 87 fa <48> 83 eb 68 74  
71 e8 a9 a9 87 fa 48 8d bb 88 04 00 00 48 89 f8 48
RSP: 0018:ffff88806485faa8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000040000 RBX: ffff88809f242a68 RCX: ffffc90005df9000
RDX: 0000000000040000 RSI: ffffffff86f6b08c RDI: ffff88809f242a68
RBP: ffff88806485fad0 R08: ffff88808e4e8700 R09: fffffbfff13fc688
R10: fffffbfff13fc688 R11: ffffffff89fe3443 R12: dffffc0000000000
R13: 0000000000000001 R14: ffff88809b212940 R15: 0000000000000000
 x25_new_lci net/x25/af_x25.c:357 [inline]
 x25_connect+0x380/0x1050 net/x25/af_x25.c:786
 __sys_connect+0x37d/0x4c0 net/socket.c:1664
 __do_sys_connect net/socket.c:1675 [inline]
 __se_sys_connect net/socket.c:1672 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1672
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4579b9
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:00007fb14afb2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004579b9
RDX: 0000000000000012 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb14afb36d4
R13: 00000000004be22e R14: 00000000004ce488 R15: 00000000ffffffff


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