[Xen-changelog] [xen stable-4.6] x86/HVM: add missing NULL check before using VMFUNC hook

[patchbot@xxxxxxx]

commit 2eb074fddbecf40e0cdac5c5fe28fb6c7b5cc371
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Dec 21 17:45:42 2016 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Dec 21 17:45:42 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 e36eefc..ec2da3b 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1620,6 +1620,8 @@ 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, 0, ctxt);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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