Re: [Xen-devel] [PATCH v1 2/2] x86/vvmx: add vmcs id check into vmptrld emulation

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 01/03/17 09:13, Sergey Dyasli wrote:
> If a guest will do vmptrld with an incorrect vmcs id:
>
> (XEN) Xen BUG at .../git/upstream/xen/xen/include/asm/hvm/vmx/vmx.h:333
> (XEN) ----[ Xen-4.9-unstable  x86_64  debug=y   Tainted:    H ]----
> (XEN) Xen call trace:
> (XEN)    [<ffff82d0801f925e>] 
> vmcs.c#arch/x86/hvm/vmx/vmcs.o.unlikely+0x28/0x19a
> (XEN)    [<ffff82d0801f602c>] virtual_vmcs_vmread+0x11/0x2c
> (XEN)    [<ffff82d0802002cc>] vvmx.c#_map_io_bitmap+0x86/0x88
> (XEN)    [<ffff82d080202399>] nvmx_handle_vmptrld+0xf0/0x1fb
> (XEN)    [<ffff82d0801fe93c>] vmx_vmexit_handler+0x132b/0x1c49
> (XEN)    [<ffff82d080203e6c>] vmx_asm_vmexit_handler+0x3c/0x120
>
> Fix this by adding appropriate checks for vmcs id during vmptrld
> emulation.
>
> Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vvmx.c        | 11 +++++++++++
>  xen/include/asm-x86/hvm/vmx/vmcs.h |  1 +
>  2 files changed, 12 insertions(+)
>
> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
> index 4f5ee5a..580fd3e 100644
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -1633,6 +1633,17 @@ int nvmx_handle_vmptrld(struct cpu_user_regs *regs)
>          {
>              if ( writable )
>              {
> +                struct vmcs_struct *vvmcs = vvmcx;
> +
> +                if ( ((vvmcs->vmcs_revision_id ^ vmx_basic_msr) &
> +                                         VMX_BASIC_REVISION_MASK) ||
> +                     (!cpu_has_vmx_vmcs_shadowing &&
> +                      (vvmcs->vmcs_revision_id & ~VMX_BASIC_REVISION_MASK)) )
> +                {
> +                    hvm_unmap_guest_frame(vvmcx, 1);
> +                    vmfail(regs, VMX_INSN_VMPTRLD_INCORRECT_VMCS_ID);

A newline here please (can be fixed on commit if there are no other
issues).  Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> +                    return X86EMUL_OKAY;
> +                }
>                  nvcpu->nv_vvmcx = vvmcx;
>                  nvcpu->nv_vvmcxaddr = gpa;
>                  v->arch.hvm_vmx.vmcs_shadow_maddr =
> diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h 
> b/xen/include/asm-x86/hvm/vmx/vmcs.h
> index 4ee01da..6308e4b 100644
> --- a/xen/include/asm-x86/hvm/vmx/vmcs.h
> +++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
> @@ -521,6 +521,7 @@ enum vmx_insn_errno
>      VMX_INSN_INVALID_CONTROL_STATE         = 7,
>      VMX_INSN_INVALID_HOST_STATE            = 8,
>      VMX_INSN_VMPTRLD_INVALID_PHYADDR       = 9,
> +    VMX_INSN_VMPTRLD_INCORRECT_VMCS_ID     = 11,
>      VMX_INSN_UNSUPPORTED_VMCS_COMPONENT    = 12,
>      VMX_INSN_VMXON_IN_VMX_ROOT             = 15,
>      VMX_INSN_FAIL_INVALID                  = ~0,


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