INFO: rcu detected stall in __kvm_read_guest_page

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 3d0e7a9e00fd Merge tag 'md/4.19-rc2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13fad421400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=8450e74691da922b1e3b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [gre...@linuxfoundation.org h...@zytor.com
kste...@linuxfoundation.org linux-...@vger.kernel.org mi...@redhat.com
pombr...@nexb.com tg...@linutronix.de x...@kernel.org]

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+8450e7...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-...!: (10498 ticks this GP) idle=c26/1/0x4000000000000002
softirq=10802/10802 fqs=1
rcu: (t=10500 jiffies g=12133 q=33)
rcu: rcu_preempt kthread starved for 10498 jiffies! g12133 f0x0
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 22872 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
schedule+0xfe/0x460 kernel/sched/core.c:3517
schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
rcu_gp_kthread+0x9d9/0x2310 kernel/rcu/tree.c:2194
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
NMI backtrace for cpu 0
CPU: 0 PID: 8238 Comm: syz-executor2 Not tainted 4.19.0-rc2+ #6
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+0x1c4/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b3/0x1ed 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:162 [inline]
rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340
print_cpu_stall.cold.78+0x2d3/0x524 kernel/rcu/tree.c:1478
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3276 [inline]
rcu_pending kernel/rcu/tree.c:3319 [inline]
rcu_check_callbacks+0xfd9/0x1990 kernel/rcu/tree.c:2665
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:1029 [inline]
smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1054
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
</IRQ>
RIP: 0010:__phys_addr+0xaf/0x120 arch/x86/mm/physaddr.c:31
Code: 0f b6 0d 7d c4 f8 08 4c 89 e3 31 ff 48 d3 eb 48 89 de e8 14 64 46 00
48 85 db 75 0f e8 da 62 46 00 4c 89 e0 5b 41 5c 41 5d 5d <c3> e8 cb 62 46
00 0f 0b e8 c4 62 46 00 48 c7 c7 10 10 47 89 48 b8
RSP: 0018:ffff88019b3c68d8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 00000001b309bf80 RBX: 1ffff10033678d21 RCX: ffffc90006ee4000
RDX: 0000000000040000 RSI: ffffffff81386c66 RDI: 0000000000000007
RBP: ffff88019b3c6a10 R08: ffff8801cf0f45c0 R09: ffffed00366137f0
R10: ffffed00366137f1 R11: ffff8801b309bf8e R12: ffff8801b309bf80
R13: 000000000000000f R14: ffffea0000000000 R15: ffff88019b3c69e8
check_object_size include/linux/thread_info.h:119 [inline]
__copy_from_user include/linux/uaccess.h:74 [inline]
__kvm_read_guest_page+0xda/0x130
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1737
kvm_vcpu_read_guest_page+0x40/0x50
arch/x86/kvm/../../../virt/kvm/kvm_main.c:1757
kvm_fetch_guest_virt+0x149/0x1c0 arch/x86/kvm/x86.c:4878
__do_insn_fetch_bytes+0x45b/0x950 arch/x86/kvm/emulate.c:896
x86_decode_insn+0x1544/0x54c0 arch/x86/kvm/emulate.c:5107
x86_emulate_instruction+0x89a/0x1f90 arch/x86/kvm/x86.c:6175
kvm_mmu_page_fault+0x342/0x1ad0 arch/x86/kvm/mmu.c:5276
handle_ept_violation+0x29e/0x6a0 arch/x86/kvm/vmx.c:7679
vmx_handle_exit+0x2f7/0x17f0 arch/x86/kvm/vmx.c:10115
vcpu_enter_guest+0x14a9/0x62e0 arch/x86/kvm/x86.c:7630
vcpu_run arch/x86/kvm/x86.c:7693 [inline]
kvm_arch_vcpu_ioctl_run+0x375/0x16e0 arch/x86/kvm/x86.c:7870
kvm_vcpu_ioctl+0x72b/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2590
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
Code: fd b4 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 b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd48488dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd48488e6d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf730 R14: 00000000004c59b9 R15: 0000000000000000
sched: RT throttling activated


---
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[Dmitry Vyukov]

#syz dup: INFO: rcu detected stall in kvm_vcpu_ioctl

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[Dmitry Vyukov]

A little bit of testing:

#syz undup

[Dmitry Vyukov]

#syz dup: INFO: rcu detected stall in kvm_vcpu_ioctl