Re: 'WARNING in handle_exception_nmi' bug at arch/x86/kvm/vmx/vmx.c:4959

[Dmitry Vyukov]

On Mon, 20 Jun 2022 at 12:25, 潘高宁 <pgn@xxxxxxxxxx> wrote:
>
> Hello,
>
>     This is Xiao Lei, Gaoning Pan and Yongkang Jia from Zhejiang University. We found a 'WARNING in handle_exception_nmi' bug by syzkaller. This flaw allows a malicious user in a local DoS condition. The following program triggers Local DoS at arch/x86/kvm/vmx/vmx.c:4959 in latest release linux-5.18.5, this bug can be reproducible stably by the C reproducer:


FWIW a similarly-looking issue was reported by syzbot:
https://syzkaller.appspot.com/bug?id=1b411bfb1739c497a8f0c7f1aa501202726cd01a
https://lore.kernel.org/all/0000000000000a5eae05d8947adb@xxxxxxxxxx/

Sean said it may be an issue in L0 kernel rather than in the tested kernel:
https://lore.kernel.org/all/Yqd5upAHNOxD0wrQ@xxxxxxxxxx/

What kernel did you use for the host machine?





> ------------[ cut here ]------------
> WARNING: CPU: 14 PID: 9277 at arch/x86/kvm/vmx/vmx.c:4959 handle_exception_nmi+0x11a7/0x14d0 arch/x86/kvm/vmx/vmx.c:4959
> Modules linked in:
> CPU: 14 PID: 9277 Comm: syz-executor.7 Not tainted 5.18.5 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
> RIP: 0010:handle_exception_nmi+0x11a7/0x14d0 arch/x86/kvm/vmx/vmx.c:4959
> Code: ff e8 1d b7 3c 00 be 0c 44 00 00 48 c7 c7 00 c9 23 8a c6 05 9f 71 5e 04 01 e8 5b 02 8d 02 0f 0b e9 64 f8 ff ff e8 f9 b6 3c 00 <0f> 0b e9 ae f4 ff ff e8 ed b6 3c 00 e8 28 97 a0 02 e9 5f fd ff ff
> RSP: 0018:ffff888038dc7b48 EFLAGS: 00010286
> RAX: 0000000000002617 RBX: 0000000000000000 RCX: ffffffff811dcf27
> RDX: 0000000000040000 RSI: ffffc90003dd1000 RDI: ffff888039595c0c
> RBP: ffff888039594000 R08: 0000000000000001 R09: ffff8880395941a7
> R10: ffffed10072b2834 R11: 0000000000000001 R12: fffffffffffffff8
> R13: 000000008000030e R14: ffff88803895c000 R15: ffff888039594068
> FS:  00007ff56edf7700(0000) GS:ffff888067d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000003aec8006 CR4: 0000000000772ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554
> Call Trace:
>  <TASK>
>  __vmx_handle_exit arch/x86/kvm/vmx/vmx.c:6239 [inline]
>  vmx_handle_exit+0x5e7/0x1aa0 arch/x86/kvm/vmx/vmx.c:6256
>  vcpu_enter_guest arch/x86/kvm/x86.c:10283 [inline]
>  vcpu_run arch/x86/kvm/x86.c:10365 [inline]
>  kvm_arch_vcpu_ioctl_run+0x2a2e/0x5ca0 arch/x86/kvm/x86.c:10566
>  kvm_vcpu_ioctl+0x4d2/0xc60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3943
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl fs/ioctl.c:856 [inline]
>  __x64_sys_ioctl+0x16d/0x1d0 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x45e8c9
> Code: 4d af 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 1b af fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ff56edf6c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 000000000077bf60 RCX: 000000000045e8c9
> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
> RBP: 000000000077bf60 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc491be6af R14: 00007ff56edf79c0 R15: 0000000000000000
>  </TASK>
> ---[ end trace 0000000000000000 ]---
>
> Syzkaller reproducer:
> # {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:true UseTmpDir:false HandleSegv:false Repro:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}
> r0 = openat$kvm(0xffffffffffffff9c, &(0x7f0000000000), 0x0, 0x0)
> r1 = ioctl$KVM_CREATE_VM(r0, 0xae01, 0x0)
> r2 = ioctl$KVM_CREATE_VCPU(r1, 0xae41, 0x0)
> syz_kvm_setup_cpu$x86(r1, r2, &(0x7f0000fe8000/0x18000)=nil, &(0x7f00000000c0)=[@textreal={0x8, 0x0}], 0x1, 0x17, &(0x7f0000000100)=[@cr4={0x1, 0x200915}], 0x1)
> ioctl$KVM_RUN(r2, 0xae80, 0x0)
>
>
> C repro and config are attached.
>
>
> Best regrads.
>
> Xiao Lei from Zhejiang University.
>
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