[Xen-changelog] [xen stable-4.8] x86/HVM: add missing NULL check before using VMFUNC hook

[patchbot@xxxxxxx]

commit 24ccfc33272be300b306873b75352c0de3deca94
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Dec 21 17:41:20 2016 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Dec 21 17:41:20 2016 +0100

    x86/HVM: add missing NULL check before using VMFUNC hook
    
    This is CVE-2016-10025 / XSA-203.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 74dcd0ce6f4fadce8093e54f0fc1a45426577e13
    master date: 2016-12-21 16:47:19 +0100
---
 xen/arch/x86/hvm/emulate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index f1f6e2f..f32b7dc 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1694,6 +1694,8 @@ static int hvmemul_vmfunc(
 {
     int rc;
 
+    if ( !hvm_funcs.altp2m_vcpu_emulate_vmfunc )
+        return X86EMUL_UNHANDLEABLE;
     rc = hvm_funcs.altp2m_vcpu_emulate_vmfunc(ctxt->regs);
     if ( rc != X86EMUL_OKAY )
         hvmemul_inject_hw_exception(TRAP_invalid_op, HVM_DELIVER_NO_ERROR_CODE,
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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