Messages in this thread | | | Subject | Re: [PATCH] KVM: x86: Fix the NULL pointer parameter in check_cr_write() | From | David Hildenbrand <> | Date | Mon, 18 Sep 2017 14:19:26 +0200 |
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On 18.09.2017 12:45, Yu Zhang wrote: > 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: d1cd3ce90044 ("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> > --- > arch/x86/kvm/emulate.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 16bf665..15f527b 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -4102,10 +4102,12 @@ static int check_cr_write(struct x86_emulate_ctxt *ctxt) > ctxt->ops->get_msr(ctxt, MSR_EFER, &efer); > if (efer & EFER_LMA) { > u64 maxphyaddr; > - u32 eax = 0x80000008; > + u32 eax, ebx, ecx, edx; > > - if (ctxt->ops->get_cpuid(ctxt, &eax, NULL, NULL, > - NULL, false)) > + eax = 0x80000008; > + ecx = 0; > + if (ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, > + &edx, false)) > maxphyaddr = eax & 0xff; > else > maxphyaddr = 36; >
Not sure if fixing kvm_cpuid() would be better.
Reviewed-by: David Hildenbrand <david@redhat.com>
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Thanks,
David
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