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

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

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);
+                    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,
-- 
2.9.3


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