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Subject[PATCH] KVM: x86: Fix the NULL pointer parameter in check_cr_write()
Date
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;
--
2.5.0
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