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KVM: x86: Fix the NULL pointer parameter in check_cr_write() 

Routine check_cr_write() will trigger emulator_get_cpuid()->
kvm_cpuid() to get maxphyaddr, and NULL is passed as values
for ebx/ecx/edx. This is problematic because kvm_cpuid() will
dereference these pointers.

Fixes: d1cd3ce900 ("KVM: MMU: check guest CR3 reserved bits based on its physical address width.")
Reported-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Yu Zhang 2017-09-18 18:45:01 +08:00 committed by Radim Krčmář
parent 95e2a3b3ef
commit d6500149bc
1 changed files with 5 additions and 3 deletions
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8
arch/x86/kvm/emulate.c
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@ -4102,10 +4102,12 @@ static int check_cr_write(struct x86_emulate_ctxt *ctxt)
ctxt->ops->get_msr(ctxt, MSR_EFER, &efer); ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
if (efer & EFER_LMA) { if (efer & EFER_LMA) {
u64 maxphyaddr; u64 maxphyaddr;
u32 eax = 0x80000008; u32 eax, ebx, ecx, edx;
if (ctxt->ops->get_cpuid(ctxt, &eax, NULL, NULL, eax = 0x80000008;
NULL, false)) ecx = 0;
if (ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx,
&edx, false))
maxphyaddr = eax & 0xff; maxphyaddr = eax & 0xff;
else else
maxphyaddr = 36; maxphyaddr = 36;