Re: 'WARNING in vcpu_enter_guest' bug in arch/x86/kvm/x86.c:9877

[Sean Christopherson]

On Thu, Mar 10, 2022, 潘高宁 wrote:
> Hello, This is Gaoning Pan and Yongkang Jia from Zhejiang University. We
> found a 'WARNING in vcpu_enter_guest' bug by syzkaller. This flaw allows a
> malicious user in a Local DOS condition. The following program triggers Local
> DOS in vcpu_enter_guest in arch/x86/kvm/x86.c:9877 in latest release
> linux-5.16.13, this bug can be reproducible stably by the C reproducer:
> 
> ------------[ cut here ]------------

...

> Syzkaller reproducer:
> # {Threaded:true Repeat:true RepeatTimes:0 Procs:16 Slowdown:1 Sandbox:
> r0 = openat$kvm(0xffffffffffffff9c, &(0x7f0000000000), 0x0, 0x0)
> r1 = ioctl$KVM_CREATE_VM(r0, 0xae01, 0x0)
> ioctl$KVM_CAP_SPLIT_IRQCHIP(r1, 0x4068aea3, &(0x7f0000000000)) (async)
> r2 = ioctl$KVM_CREATE_VCPU(r1, 0xae41, 0x0) (async)
> r3 = ioctl$KVM_CREATE_VCPU(r1, 0xae41, 0x400000000000002)
> ioctl$KVM_SET_GUEST_DEBUG(r3, 0x4048ae9b, &(0x7f00000000c0)={0x5dda9c14aa95f5c5})
> ioctl$KVM_RUN(r2, 0xae80, 0x0)
> 
> C repro and kernel config are attached.

Reproduced, should have a fix posted shortly, thanks!