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SubjectRe: [PATCH v2] KVM: X86: Fix SMRAM accessing even if VM is shutdown
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On 08/02/2018 08:32, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> Reported by syzkaller:
>
> WARNING: CPU: 6 PID: 2434 at arch/x86/kvm/vmx.c:6660 handle_ept_misconfig+0x54/0x1e0 [kvm_intel]
> CPU: 6 PID: 2434 Comm: repro_test Not tainted 4.15.0+ #4
> RIP: 0010:handle_ept_misconfig+0x54/0x1e0 [kvm_intel]
> Call Trace:
> vmx_handle_exit+0xbd/0xe20 [kvm_intel]
> kvm_arch_vcpu_ioctl_run+0xdaf/0x1d50 [kvm]
> kvm_vcpu_ioctl+0x3e9/0x720 [kvm]
> do_vfs_ioctl+0xa4/0x6a0
> SyS_ioctl+0x79/0x90
> entry_SYSCALL_64_fastpath+0x25/0x9c
>
> The syzkaller creates a former thread to issue KVM_SMI ioctl, and then creates
> a latter thread to mmap and operate on the same vCPU, rsm emulation will not be
> executed since there is no something like seabios which implements smi handler
> when running syzkaller directly. This triggers a race condition when running
> the testcase with multiple threads. Sometimes one thread exit w/ SHUTDOWN
> reason, another thread mmaps and operates on the same vCPU, it continues to
> use CS=0x30000, IP=0x8000 to access the address of SMI handler which results
> in the above ept misconfig. This patch fixes it by returning RET_PF_EMULATE
> in kvm_handle_bad_page() which would cause an emulation failure and then an
> exit with KVM_EXIT_INTERNAL_ERROR, the VM will stop instead of resetting and
> be taken advantage of.
>
> Reported-by: syzbot+c1d9517cab094dae65e446c0c5b4de6c40f4dc58@syzkaller.appspotmail.com
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> v1 -> v2:
> * return RET_PF_EMULATE
>
> arch/x86/kvm/mmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 8eca1d0..6c5a82c 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3029,7 +3029,7 @@ static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)
> return RET_PF_RETRY;
> }
>
> - return -EFAULT;
> + return RET_PF_EMULATE;
> }
>
> static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

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