Re: [PATCH] KVM: x86: fix fixing of hypercalls

["Radim Krčmář" <rkrcmar@redhat.com>]

2017-01-17 14:51+0100, Dmitry Vyukov:
> emulator_fix_hypercall() replaces hypercall with vmcall instruction,
> but it does not handle GP exception properly when writes the new instruction.
> It can return X86EMUL_PROPAGATE_FAULT without setting exception information.
> This leads to incorrect emulation and triggers
> WARN_ON(ctxt->exception.vector > 0x1f) in x86_emulate_insn()
> as discovered by syzkaller fuzzer:
> 
> WARNING: CPU: 2 PID: 18646 at arch/x86/kvm/emulate.c:5558
> Call Trace:
>  warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
>  x86_emulate_insn+0x16a5/0x4090 arch/x86/kvm/emulate.c:5572
>  x86_emulate_instruction+0x403/0x1cc0 arch/x86/kvm/x86.c:5618
>  emulate_instruction arch/x86/include/asm/kvm_host.h:1127 [inline]
>  handle_exception+0x594/0xfd0 arch/x86/kvm/vmx.c:5762
>  vmx_handle_exit+0x2b7/0x38b0 arch/x86/kvm/vmx.c:8625
>  vcpu_enter_guest arch/x86/kvm/x86.c:6888 [inline]
>  vcpu_run arch/x86/kvm/x86.c:6947 [inline]
> 
> Set exception information when write in emulator_fix_hypercall() fails.
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Wanpeng Li <wanpeng.li@hotmail.com>
> Cc: kvm@vger.kernel.org
> Cc: syzkaller@googlegroups.com
> ---

Applied to kvm/master, thanks.